I see an older video card that I've seen failures at the shop too many times.
Let's try something typical. Did you open up this PC and use your canned air to clean off the video card and other heat sinks in the PC?
If your reply is no or "what is canned air?" then maybe it's time to get this yearly cleaning done.
windows xp home edition sp3
intel core 2 cpu firstname.lastname@example.org 997mhz
nvidia geforce go 7600 video card
monitor turns on and off repeatedly, seems to happen more so when something on screen changes such as window opening or something moving in a window, installed all update avaliable have tried old and new video drivers all do the same. thinking it is a hardware problem just would like some opinions