The Screen Will Now Pause When The Sound Does?

my system has been skipping for a bit now, basically a few things are quite wrong to me, and them seem to get worse. in chronological order;crackling in the sound (i use optical audio with the z5500 speakers from logitech) small jitters/pauses from time to time jitters/pauses got longer and more frequent video card crashing (im guessing caused by drivers)** very long pauses all video is affected (Internet causes a massive pause after about 30seconds, window goes green - flv player crashes/gets lines across the window) *note: when it the video jitters, so does the sound**what i mean by crash is, the screen will go off completely (as if in sleep mode), recover and the message will appear in the task bar saying the driver crashed.system resources will go to 100% for a brief moment while the system is unresponsive (all cores and memory to 100%). after a cold boot, it will not start for about 10 minutes, then it will start slowly and within an hour get to where it is regularly.

the computer itself is fairley new (june 2011), the hard drive, though is from 2008, i used it on another build and basically recycled it, (reinstalled the os multiple times since i bought it, clearing the drive each time.)things i have tried;kaspersky full scan ccleaner disk fragmentation disk check updated all my drivers boot to only necessary programs with msconfigmy system;os version: microsoft windows 7 ultimate, 64 bit processor: intel(r) core(tm) i7-2600 cpu @ 3.40ghz, intel64 family 6 model 42 stepping 7 processor count: 8 ram: 8174 mb - g.skill ripjaw series 1600 graphics card: nvidia geforce gtx 570, 1280 mb hard drives: c: total - 476836 mb, free - 103627 mb - wd caviar blue motherboard: asrock, p67 extreme4 antivirus: kaspersky pure, enabledi have gotten several error messages in korean from chrome, not sure what exactly they were saying. the screen will now pause when the sound does, then after a little while it will go back to normal but not before having the whole screen go black.