Need help - big problem with sound (interrputs etc.)

[beeblebrox]

Hello experts,
i need your help on software on the T40p.

I am using iTunes 4.7.1 playing music from my external hdd.
Never had any problems with that.

The past few weeks I did a larger project on scanning a few thousand slides with a special scanner, using Silverfast software, which frequently crashed. I always had to use a Windows cleaner (TuneUp Utilities 2004) afterwards.

Now I suddenly have the problem, that I can not use iTunes (or Windows media player) in the background anymore, or even as a stand alone program.

The symptoms are stuttering, short repeats of music fractions, very much like missed frames etc.
If I turn on the visualizer (in iTunes or media player) I am not able to listen to music anymore, because if the interrupts every now and then (always with high CPU usage for the graphics or anything else going on)

I de-installed/re-installed iTunes and media player several times, did a diskcheck, re-installed the audio drivers. Gave priority to programs and/or system cache. No success.

Even my old T20 is capable of playing smooth music. It continued playing music for a while, even when windows crashed.

I am soooo frustrated, I just can't find out what is screwed up in windows. Anybody can help here?