Nashy

This is my seventh day of trying to isolate the problem but I dont have a clue what's going on. I bought a new pc and hitman contracts and I can't even play a dvd. I'm so gutted please help The problem: Firstly I noticed Hitman (the game) was crashing so I started tweaking graphics options etc in the game...but I later leaned that I couldn't play a dvd either. At some random point between 20-300 seconds into the dvd, everything freezes. I can't move the cursor or ctrl + del + alt. and it's so annoying. I've done the following. 1) re-installed win xp proffesional (clean install total of four times now) 2)re-installed driver for video card (readeon 9600 256ddr) 3)re-installed driver for nvidea onbaord sound 4)re-installed game 5)re-installed power dvd 5 (software I use to run dvd's) 6)updated all drivers 7)installed patch for game now it got nasty 8)ventured into bios and tweaked apature to 256mb 9)tweaked agp 8x speed to 4x in bios 10)disable agp fastwrite in bios 11)switched off vpu recovery in ati control panel (on desktop) 12)turned off 'sticky keys' (win xp feature) 13)turned of agp write in ati control panel (on desktop) My computer sometimes randomly restarts for no reason or freezes even on the desktop. I searched for a virus but came up with nothing. I used 'spybot', 'the cleaner', 'pc-cillin' and links on the xp website to tackle popular virus's that were not present anyway. I suspected that my processor was too hot but bios said it was nominal and it wasn't being overclocked (amd athalon xp3200+). As a result i decided to set default bios settings and for a whole night I could play hitman. I even watched half an hour of a dvd at 4 in the morning just to test out my new baby but the next day my computer wouldn't turn out without showing a black screen and a slow but repetative beep from the mother board. I phoned up pc world (of whome i didn't buy the computer off might I add), and they said the beeping might have something to do with my RAM. After resetting the cmos manually by taking out the motherboard battery etc, i loaded up xp on the default bios settings again then turned off the comp and swapped my ram chipset's around (1024MB - two chipsets). That had no effect. I've run scandisk and disk defragmentor and this hasn't solved the prob either. I've tried 3 different video cards (old ones and new ones), 3dfx voodoo4, ati radeon 9200 and the one at present (powercolor radeon 9600 256ddr) and still no luck. btw my motherboard is asus. I know this is a long entry but I hope someone can help me out. I've voided the warrany on my computer because I've taken the sticker off the back to open the case so I can't take the computer back now but I'm hoping this is a software problem or even a minor hardware problem that can be easily solved with your guidance. I'm running out of ideas as to what this could be. I'm all ears. Reagards Nashy