Same problem with DVI and D-SUB: so it's not the cable or the digital-analog converter for the D-SUB port or in the monitor.
I cannot see how wrong drivers could do this, the GPU is part of the processor so the chip is most likely allright.
1a) check the monitor itself with from a completely different image source
1b) using stand-alone GPU (
don't buy any!!!) could yield more info too
2) somebody suggested PSU as a possible source of your woes,
have they not?
I learned the hard / exhausting way in January and February, that for 100 quid one can have a brand new machine faster than the old one, a very reliable and quiet one too. Much wiser choice than patching up old components.
take care, FD.