(1) Acer Aspire 5542 5241, AMD Turion II Dual-Core Mobile M500, 4Gb RAM
(2) Bangho (the argentinian name for Chinese Clevo) Intel Pentium CPU 2020M @ 2.40GHz, 8Gb RAM
(3) Gfast (an Argentine brand for some Chinese generics) Intel Core i7-4710MQ @ 2.50GHz, 8Gb RAM
(4) MSI GL62M Intel Core i7-7700HQ @ 2.80GHz, 8GB RAM

On laptop (1) Pianoteq run smoothly in Windows 7 64bits at 44100KHz with the internal sound chip and ASIO4all, selecting the minimum buffer size. Only Pianoteq, no  other programs. WiFi had to be deactivated*.
Sometimes CPU got overloaded, but it was playable in general. The computer would get hot from time to time, with a constant CPU load over 60-70% while playing.
One sad day, the CPU got burnt (not while using Pianoteq).
I could not manage to make it work in GNU/Linux (tried ALSA / pulse audio / JACK, 32 and 64 bits). In any case, I would get lot of pops, clicks and CPU overloads.

Computer (2): I could use internet and other programs while playing, it worked very well in Ubuntu Studio (64 bits), I could whatch YouTube as I played, using 'pulse audio'.  Usually I used ALSA directly. Never installed Windows on this laptop while being used for Pianoteq.
Sometimes Pulse Audio changed the sound card frequency and the sound got distorted and the pitch transposed...
This was a very generous setup, in the sense that I got lot of red lines in the performance tab of Pianoteq options but the sound never went away, even if I tried to by playing lot of bass chords and notes with damper pedal (at least at 44.1/48 KHz).
I reactivated CPU frequency scaling (ubuntu studio fixes the cpu to max freq) and the system worked properly.

For (3) with Ubuntu Studio, I could set the frequency to 192KHz and the program would play well. I used to open two instances of Pianoteq to have, with an external sound card, more outputs, and it ran flawessly. Only one issue: WIFI and Pianoteq again not compatible*.
Latter I installed Windows 10, and the performance was much poorer than in Linux. The program detects overload and mutes if I use much pedal, even though windows task manager says there is about 5% of CPU load. A little message saying that CPU is not powerful enough or my power saving settings are too aggressive pops up, even if the energy plan is set to high performance .

I have had (4) for only a few weeks, and the behavior is very similar to (3), may be a little better, with a no minor improvement: I can connect to WIFI. I have used only Windows 10, perhaps I will install Ubuntu Studio later to compare.

I don't know if it true, but for some reason I feel that the Acer laptop had the best sound of all.

Based on my experience, the order of perfomance seems to be W7 > Ubuntu Studio > W10. Anyway this order is based on particular cases.

More tech details (I don't know what is more relevant for Pianoteq)

CPU        Clock        Cores    Threads        L1 data        L1 instr.        L2             L3        Bus sp.         RAM cl.        Thread PassMark        CPU PassMark
m500        2.2GHz        2        2                2x64KB        2x64            2x512KB        -        3.6GT/s        667MHz        744                        1307
2020m        2.4            2        2                2x32        2x32            2x256            2MB        5                1333            1253                        2298
4710mq        2.5**        4        8                4x32        4x32            4x256            6            5                1600            1897                        7995
7700hq        2.8**        4        8                4x32        4x32            4x256            6            8                2400            2027                        8984

*The WiFi issue may be due to interrupts on the same IRQ than sound card, I remember they could be changed in Windows 95, but I could not do it on Windows 7 (there was a very funny W95 hanging event if you tried to use a diskette while playing music... this could be avoided if IRQ of the diskette was set different than the sound card).
**Those CPU feature 'turbo boost'. For (3) it is disabled since the motherboard doesn't support it. A core in case (4) can go up to 3.5GHz.

Virtualbox (Sun/Oracle) running as a program on Linux provides a virtual machine interface - in which you can run Windoze; ALL versions AFAIK, certainly from Vista on including W10, although I have NOT personally tried W8.
There is a less than 5% performance penalty on my (not very accurately controlled) fairly large compilations (a couple of Gig of code, not music) experiments.
There is a seamless mode that may make a more complete illusion of windows programs running "clearly and transparently" under Linux, but I haven't used that to any extent.

It may be worth a try, I have run Pianoteq only on native Linux directly, I would expect it to work within a few percent as well under Linux/VirtualBox/Windows as it is able to on native Windows.

Basically "Windows doesn't know" that it isn't running directly on hardware, it is presented with a virtual machine interface that "looks/feels exactly like" hardware.

There is a "but" and it can be a BIG BUTT if you don't have much physical memory on the host machine.
Virtual machines need to have memory set aside for them, whether they use it or not - at least in the current implementation of VirtualBox.
I don't know what W10 wants/needs, but VirtualBox suggests 2 Gig RAM when it creates a new virtual machine.
The point is you may have to trade off host for guest performance, or vice versa.

... if Pianoteq can be substituted to qsynth (for the piano) and communicate with Rosegarden through Jack ...

Well out of curiosity I just tried this and got Pianoteq to work as an instrument fed by Rosegarden and to record from my keyboard on Rosegarden and play that through Pianoteq.

By default Pianoteq will "listen on all inputs" and you need to go into "options" to just link it to Rosegarden or it will picked up the keys you press on your keyboard and play a note for that and also play the same note when Rosegarden send it's request to play a note after reading the same key press.

QJackCtl seems to work OK by default (for some reason I'm always surprised when that happens).  As usual order of starting things seems to make a difference.

Rosegarden was a bit shy about selecting devices and seems to know about Pianoteq's midi input sinks (as it should), so it can play sounds using Pianoteq, but you may have to force it to choose those devices.  Maybe this works automatically when you've done your initial setup, but it would drive me bonkers if I had to do that every time and so far I've had to.

As I don't use Rosegarden I'm not sure what happened but my one gripe was that it seems that when you record it plays some sort of "tempo" sound by default (that can be disabled in Rosegarden I see), but with my basic setup it played a full piano note (through Pianoteq !) as that tempo sound (not recorded in the midi file) rather than a nice tick-tock or whatever.  I think you can in theory map this to e.g. a synth, but there's no default way I can find to access something basic as a metronome sound.

I tested this by :

* Loading a midi file of moonlight sonata into Rosegarden and playing it.
* Starting a new midi file and track and hitting random keys in a most unmusical manner to record.
* Recording multiple tracks.

I found out you can map program changes (map GM midi program numbers to instruments) using the option->midi and that works, but from what I can see Pianoteq only respects one of those program numbers at a time (so no using different instruments for different tracks).  So while I could happily switch from program 1 (mapping to a D4 FXP) to program 2 (mapped to one to the Grimaldi Harpsichord presets) when I created separate tracks for each program Pianoteq just acted on one program change (presumably the last one it got from Rosegarden) and played that (which worked out as the D4 variant).  Maybe that can be worked around (multiple instances of standalone Pianoteq ?) but I don't know how at present.

Having Pianoteq on Linux is of no consequences, having all those best seller softwares ported on Linux would be fatal.

Since you are using Linux, regarding Jack, lately I was using qsynth and Rosegarden simultaneously (with JACK), qsynth as the soundfount player for what is being produced on Rosegarden. If Pianoteq can be substituted to qsynth (for the piano) and communicate with Rosegarden through Jack... that would be a very powerful tool (I haven't tried this yet, but plan to if I have time). Rosegarden supports a lot of things like pitch bend (while musescore doesn't even read them).

Hope such a thought never cross the evil mind of software companies.

I feel obliged to point out that if you're using Pianoteq on Linux you are using commercial software from a one of those evil minded software companies. :-)  I know I am.

On Linux JACK is roughly equivalent to ASIO - a low latency sound API.  JACK is typically either installed by default or easily installed from software repositories in most Linux distros.  Pianoteq does support JACK on Linux (AFAIK) but I normally use ALSA and PulseAudio as I don't usually run a DAW or need other JACK-related stuff.

You can run some Windows software moderately well using WINE, which provides a kind of Window's compatibility layer.  It's also widely available  from mainstream distro respositories and installs easily.

If you use Steam (games) then you can run some of those either natively in Linux (where available) or using Wine (there's PlayOnLinux to help with that or CodeWeavers do a commercial version of that).

In fact, would all my windows-software run with a Linux machine, and would something like ASIO be included, running as fine as it does in Windows, I would totally forget about Windows.

Will never (I hope) happen (all your Windows softwares), it's not the real mandate of Linux. If all those paid softwares migrated to Linux tomorrow, it will be a blow to Linux and the open-source community at large. Hope such a thought never cross the evil mind of software companies.

Just to complete this posting, despite all your wonderful advice for which I offer a grovelling apology, I continue to use my existing (Vista) system now totally detached from the internet; installation of additional Pianoteq stuff comes from a memory stick which works well.

If it works . I had pianoteq for 6 years on a Vista machine and never had a problem (Vista had 57 or abouts background services running, I cut those to about 20, got rid of UAC and after some more things I forgot it worked wonderful, years without 1 crash - even if of course Win7 was much, much better right from the start).

In case you would ever try Linux, I run Lubuntu now on an old lappie. That is the lightest version of Linux you can get, needs lesser resources than all others up to now. By the way - always nice to have some of those oldie laptops without the horrible apple-idea of built-in batteries, is it . Things run for 15 years with a cheap replacement battery, and in 40 years people will shout about us and our wasting of billions of machines.

Must do some tests with Linux and pianoteq - I never had pianoteq running with Linux up to now, but Lucy suggests it is working good. Setting up Lubuntu (or whatever Linux version) is really easy these days, re-installing far easier than with Windows. And my USB2-soundcards work wonderfully with it. In fact, would all my windows-software run with a Linux machine, and would something like ASIO be included, running as fine as it does in Windows, I would totally forget about Windows.
It is nice that pianoteq works with Linux out of the box. Reaper does, but via "Wine", a kind of "box in between" to simulate Windows in Linux - and that is not as good as original Windows.

Well, whatever - nice that it works for you . My 2007 Vista machine still runs with the latest Pianoteq, without 1 dropout. Another wonderful thing about the software, if you can still use it hassle-free 11 years after you bought a laptop .

And I just  . . . sit down and play the thing.  Like you do with an acoustic.  Happy days!

If you want to try Windows 10, I encourage you to try some free tutorials and software ( e.g. https://www.oo-software.com/en/shutup10 ; https://www.safer-networking.org/spybot-anti-beacon/) to help you to run windows 10 in a better privacy environment.

Have you tried a live Linux distro? you could get the feeling without making any changes to your system. Try it; you have nothing to lose except a few minutes.

Now, since I installed Pteq 5.8.1 and those antique freebies, that's gone belly up for the first time, too.  All settings gone crazy,  looks like a job for tomorrow . . . .heh ho said Roly . .

Many don't like the idea of not having the liberty to chose individually what they want and don't want.

Also, I wouldn't ditch Windows this easily, Linux (in practical) isn't meant to replace Windows, and will never will. Some material support or softwares require a lot of ressources to just be maintained open source, or low budget. Also, when patents are necessary there is no alternatives.

Where possible substitute, that's where Linux shines... it is in the underground work, where it takes much less ressources... to then finalize it under Windows with minimal self imposed restrictions. The thing is to maximize productivity by using each where they are most efficient.

Also, there is considerable differences between Vista and on the other hand 7/10.

It seems to STILL be the case that every hardware speed increase gets eaten up by Windoze layered bloatware, so W10 on a new machine probably gives little actual performance increase over Vista on its then contemporary hardware.

Totally wrong. Vista was abysmal.

Can we say "feature encumbered" ?

Anyway, Ubuntu and its derivatives released the April 2017 edition TODAY !
One of my faves is UbuntuStudio, the current version is 17.04  {Which reflects the year and month}
More than just Linux, it has some fun Video, photo, graphics, audio tools as well.
Not embedded, so they only use resources when they are run.

Go here; http://cdimage.ubuntu.com/ubuntustudio/...y/release/
Burn it to a DVD, back up winoze if you have anything worthwhile on it.
Boot the DVD, shrink your windows partition, create a new one for Ubuntu - and follow the rest is essentially automatic.

You will find "look and feel" differences between this and Vista, but probably no greater than between Vista and W10.