Boot Problems Scratchy Sound and more HELP !!!!

I've got a new PC. Dual Core with 2 Gb Ram. I installed all my programs on
it. After 4 days the PC hung up. After i restart, booting took around 4 - 6
minutes. And the windows sounds and sounds from games sounds scratchy. When i
play music and i open a window like control panel i gets more scratchy. I
installed again and after 4 days the same thing. During a 3D game i heard the
ingame sound very scratchy. And i had Problems to leave the game with the ESC
key. I had to end it with the task manager. It takes again a long time to
boot. what could that be? can somebody help me. Is there a windows file that
grows up?

Please HELP