god, dont uninstall graphics drivers if you dont know how :S
sabertooth doesnt have igp does it?
sigh.... if you have your instalation disc somewhere you can run fix using it
or if you get past bios with display then boot into safe mode, it should ignore the drivers and use default ones it can find. then just re-install them in there if you can.
a new retail card shouldnt artifact no matter the circumstance, atm its pointless until you sort out the drivers bsod issue but what artifacts are they, did you check your monitor connection? checked that it sits in the slot properly?
also drivers wouldnt cause artifact on low gpu usage anyways.
a 500w should handle the load as well
hmmm :s