hey. well, when you install drivers the gpu will be able to ramp up to its clocks, so if the pci-express power
connector is not there it wont be able to work. can you check on that?
if not, then probably you need to use driver cleaner in safe mode, again.
are you getting the drivers from xfx's or amd's website?
AMD Graphics Drivers & Software ATI Radeon
those are for windows 7 if you use another os you need to get the appropriate set.
how about this, if it stil ldoesnt work..
in safe mode, get
Download | Ubuntu
and put it on a cd/dvd. after that, boot the computer with it.
if no issues, its just software. if issues, may be hardware related,again check the
power connector