When processing any graphics based program it will run for a few seconds and then the screen freezes. I switch off, unplug the power cord and press the on switch to switch off fans etc. When I re-plug the power cord, switch on and start the PC, the buzzer on the motherboard beeps for about a second, goes silent and beeps again. Usually the second time I go through that process the PC starts and works OK. The only clues I have are two errors registered in the event log - events 7000 & 7026.
I have recently installed the ATI Radeon X1650 pro display adapter and increased ram from 512 Mb to 2.0 Gb. All drivers are up to date.
In an attempt to get round the problem I have tried uninstalling the Radeon adapter and replacing it with the original nVidia one; but with this I cannot even get the PC to boot into Windows.
I have a number of system back-up drives, which I have also tried; again to no-avail.
Any help would be much appreciated