Video problems

I am runnning winxp pro and I am having some major problems with my display. My image on my screen (ie. screen size) keeps growing and shrinking at intermitent times. It is really annoying.
I have tried changing video cards from a pci voodoo 3 2000 to a 3d blaster banshee thinking that might be the problem but it did not help, it still does it.
I thought it might be because my cards were overheating, cause they get very hot, so I bought a fan to cool then down and that did not help.
I switched monitors and that did not help.

This has been doing this for a while even when I had win98 running.

If anybody has any ideas i could use the help.

Thanks

Zeke_cl

 

could be a bad power supply in the pc, pretty strange.

Although I would think the machine would crash when it happened.

 

How large is the power supply?

What you might try is to disconnect any extra hard drives, cd/dvd/cdrw and run it that way for a while to see if the same thing happens.....