really old macbook 1.8 ghz core duo just works...

...and what is the purpose of this thread? None, if you are honest. Frustration is sometimes understandable, but it serves absolutely no purpose to start another "my OS is better" flamewar. If OS X works better for your purposes: that's the reason there are multiple Pianoteq flavours in the first place (there is even a Linux variant, BTW). So use the Mac version and be happy it 'just works' . And please, stop trolling. Thanks.

I installed PT on 4 different Windows computers from weak Intel Atom netbook to 4,5 GHz Intel i5.
Win 7 and Win 8 (both 32bit and 64bit).
With build-in sound card, pci Audigy and external usb sound card.
And never had any issues.

Problem must be between the chair and keyboard :-)

Threads like these would probably belong to some "supercool fashion" sub-forum where we'd discuss that a red Schimmel is of course sounding "more sunny" than a wooden Baldwin upright, or ice-cream doesn't harm Linux while it makes Windows flubby.
A very old dual core Windows Vista laptop ran always fine with Pianoteq - this is in fact a success for the developers who manage to make a software piano that does not need the "I have to buy a new machine every year"-ideology.
In fact would there be one piano inbuilt that would in theory work in 27 years still with a PC/mac/Linux of today, that would be wonderful, and somehow similar to old pianos .

Is that wood enough?

For the record, my comment here was totally T-I-C...I have no problem with the sound of Pianoteq, it is fantastic. Just making fun of the constant call for more woodiness, something which has perhaps died down now that version 5 came out.

Linux user here since the mid 90's, and i must agree that windows is nothing but headache after headache after more headaches. Every OS has its good and bad points, except windows which has no good points. Other than marketing. I find it apalling that such deficient garbage has over 90% of the market share in operating systems.

If someone wants a good computer, easy to use, reliable etc.... i always say "get a mac".

"here's your sign"

The 3 OS options look like something this:

MacOS -- works perfect every time but it costs more money.

Linux -- it either works perfect or never works.  Audio drivers reside at the kernel level and Linus Torvalds is a total asshole about the quality of code that goes into the mainline tree.  Linux is especially good with old hardware because drivers continually accumulate as loadable kernel modules.  If your Sound Blaster 1.0 worked in Linux back in 1996, the latest Ubuntu LiveUSB will detect it because the kernel module is still there.   Linux is NOT good with the newest hardware though because even after the drivers are done, the kernel update might not make it to your distro anytime soon.

Windows -- drivers are written by individual manufacturers at varying code & testing quality.  Hardware version 1.5 with drivers 3.5.0.1 might have worked fine with Windows 7 SP1 but now you're using SP2 or Windows 8 Update 2 + drivers 3.76 + updated applications -- let's just say we've already seen in the ASIO update thread there people are saying leave well enough alone if you have a working Windows config.  Good luck hunting down drivers for out-of-support hardware -- I remember Logitech simply deleting the drivers for older hardware off their website so when I had to do a Windows reinstall, I had no choice but to buy replacement hardware.

There is one other option -- ChromeOS hardware.  This is the cheapest possible dedicated Pianoteq computer with Google subsidizing the prices.  For example, an Asus Chromebox sells for $140 .. an equivalent Intel/Gigabyte NUC w/ memory+SSD would be $250.  Same thing for an Acer Chromebook C720.  I've seen those on sale for $180 while cheapest equiv 11.6" netbook is at least $100 more.  Of course, ChromeOS won't run Pianoteq ... not until you install Crouton+CrUbuntu so you need to be tech-oriented to choose this option.

That is so untrue. As anything man-made, even Macs aren't impervious to crashes or "stupid behaviour". Seen it happen before my eyes more than once, too.