Weird (and rather dull) computer display question...

OK, one of the XP pro machines I support kept spontaneously rebooting - often never even getting as far as login; I’ve tried reseating everything, checking the fans, scanning for malware etc. The only thing that would seem to hold it off for a while was to do a system restore, but after a day or two, it all starts again.

Anyway, that’s pretty much irrelevant; I decided to give it the clean wipe and reinstall, as the next option. This machine has Novell Netware client installed, so instead of the XP welcome screen, you get a black screen with a red and grey Novell login box in the centre. I’d managed to boot as far as this login box one time, then I gave up, powered down the machine and moved it to the maintenance bench. Just to get the current data off the hard drive before wiping, I decided to boot from a Mandrake Move CD - (a ‘live’ distribution of Linux that requires no install); at the point that the Linux boot sequence switches display modes from text to graphics, the screen went black and for a fraction of a second, the greay and red Novell login box flashed into view, partially obscured by some weird chunky pixellated/coloured blocks.

Wuh duh fuh?

How did this happen? Just to recap - the machine was booted as far as the Novell login, shut down and disconnected from mains power, then booted into Linux, wherupon the Novell login box (which belongs to a Win32 service) appeared briefly on the screen. I’m guessing I was only seeing a picture of it, not the actual thing, but… but… Any suggestions?

Residuals in graphics memory, pretty common. Unusual if the machine has been disconnected from power, but not impossible.