No display after splash screen

Hello,
I switch on my Athlon 4200+ pc and i get the bios screen and then the vista bar starts to go across the screen. The screen then goes blank apart from the mouse cursor in the middle of the screen (which i can move) but the rest of the screen is blank.

I've removed the graphics card and used the onboard graphics but still get the same thing. Also disconnected dvd drives etc

Thanks!