Random crashes 3 types

Hi im running an alienware ALX, windows 7 64 bit, crossfiring a ati radeon 7800 series.

my first crash would be the screen goes into power saving mode, and all my programs are still running, but i cannot turn the screen back on

my second crash is similar but the screen goes into power saving mode, but im not sure if the programs are still running. my speakers goes crazy, a 1 sounded beep that beeps really fast.

third crash, my whole computer crashes and the fans are blowing really hard.

any intel that would help me fix this problem would be greatly appreciated.

Some additional info that ive gathered, which i dont know would be much help would be:

1. ive subscribed to iolo and it would tell me the crash types and these came up : iolo system machnic, mcafee on access scanner service, pcdrsysinfocsmi.p5x (ive unintalled pc doctor from my computer), and mcsvhost.exe
2. ive cleaned my computer of registry errors
3. scaned my computer for viruses using mcafee
4. Used stinger by mcafee and no treats found
5. used tdss killer and no treats found
6. reformatted my whole computer