I witnessed a very strange behavior with my XP Sp3. I have a program I wrote that takes the audio input from waveIn and sends to waveOut (i.e. low-level sound input playback). All that is done through two synchronized threads and everything works fine when PC is active. But when I leave that computer unattended and the screen saver kicks in, after awhile my sound playback gets totally out of whack. Obviously I cannot debug it since then PC becomes active and the program works without a hitch in that mode. (Just as a test I kept moving the mouse cursor once in a while for about an hour and the described issue didn't happen.)

Does someone know if XP SP3 lowers the thread/process execution priority while machine is idle, and if so how to avoid it?