Before the following there were no problems.
My system is a Asus P6T deluxe V2 Board, I7 9.20, 12GB Gskill ram
crossfired 4890's, Soundblaster audio card,
1000 Watt Corsair, 2 years old
Problem stated about a month ago when I swithed out a older DVD burner
for a SATA, ( I had a few old burned DVD which could not be read,)
the new DVD read most but not all, One in particicular I just let it read for a while
with limited sucess,
Couple of days later I had a reboot or a black screen, cannot remember which.
overtime this occcured, more and more frequently,
so I unplugged the burner, no difference
reinstalled Win7 64, still reboots or black screens
checked memory with memtest, passed
removed win7 HD, no difference
different Power supply no difference
cleared Cmos, new battery, no difference
attached monitor to other video card , no difference,
the only thing that made a difference was to switch to a Nvidia card
which reboots and black screeens, but not nearly as often as the ATI,
with the ATI it's almost immediate, Nvidia, days
I have given a friend both my ATI cards, and he has no problems at all
The reboots and Blackscreens are ramdom, I''m not stressing the machine
at all when they happen. the last reboot with the ATI cards
happen after the windows logon on
My thoughts are it's the Motherboard.
any help would be appreciated.