New here, having some audio problems?

[rift]

I am new to the whole computer recording thing, but I'd like to get into it. I run Pro Tools 8.0.3 through a DigiDesign MBox with an arbitrary instrument. The sound is okay at first, but quickly becomes more distorted, almost a glitched sound. It gets worse when adding things like compression or distortion onto it. When it is happening, if I quickly take the instrument down to 0 volume, I can still here the glitch sound.

My specs:
Intel CoreI7 Q720 @1.6GHz
4g ram
Windows 7 Ultimate 64 bit

Does anyone know what my problem could be?

[ondruspat]

Have you read this thread yet??

http://duc.avid.com/showthread.php?t=300050

It has the links to the optimization and troubleshooting pages. If you can't tweak your system using that information then post a SANDRA report on your computer (instructions also linked on that page)