If you search the Forum, you'll find a few threads on "optimizing Windows".  They may be helpful.

.  Charles

My performance level runs between 40 and 50. If I am just playing the piano, with instruments older than the Grotrian, I have no issues. If I am playing Grotrian, and the computer is doing absolutely anything else, such as if I am making adjustments with the mouse on the screen, running a video or playing music from an Internet page, etc., the audio level graph jumps from a nice reasonable yellow bar that is 10 – 30% of the way up the scale to creating full-height red spikes heard as audible pops and clicks. It seems to make no difference whether I turn CPU autoload detection on or off. If I do not want such behavior (such as if I am trying to play and accompaniment to something on YouTube video, or if I am just sitting and reading email while idly giving my brain and fingers something else to do in the background, I have to reduce the Pianoteq internal sampling rate to 22050 or less.