win Vista and nvidia 7900gt card problems

Hi i know there was a similar post about this issue but doesnt seem to have
been anwsered. Jist hoping spmebpdy has found a work around ?
when vista boots up to the desktop screen goes garbled have to send comp
into sleep mode blindly, bring it back out switch users and log back in and
everything is fine untill i try to play Halo2 when the game starts i get the
same screen, i have resently found out that if i start a game blind (with
out being able to read the screen) that the graphics driver sometimes crashs
and when it recovers i have a perfect screen in the game well almost perfect
its a bit jumpy, first time this happened i got the B.S.D , the second time
i try'd it, it worked fine havent been able to recreate it since.
i have updated everything on this comp. that i can think off e.g graphics
card, motherboard etc. the first time it crashed (B.S.D ) during the game i
sent an error report to microsoft which must have been about 20MB cuz it
took about 30mins to send and they sent me back a report saying this issue
has no nkown solution ??

Vista 32-bit
Nvidia Geforce 7900 GT/GTO (driver 6375 also using DVI connection )
Flat panel monitor => native res 1280 x 1024
1 GB of RAM ( I will be increasing this and game has ran fine on this
previously on Vista)
MSI K8N Diamond Plus Motherboard (nvidia nforce based board)
AMD Athlon 64 X2 dual core 4300+ 2.21 GHz
SB audigy (which works fine for me all the bells and whistles)
SATA HDD (which i might add is beging listed in device manager as a scsi
drive ?? but that for another post i guess)

Any thoughts or help appr.
Regards
John