OT Laptop Oddness

My Toshiba Laptop (running XP) has suddenly turned the display into a
colour negative. Everything else is usable just difficult to read.

Is it a setting gone haywire or physical damage? I can't recall if
its been knocked, dropped or squashed.

Any ideas to get it back to normal?

Hook up an external monitor and see if that's the same. If so, suspect the
video driver or hardware, try reloading the driver. If not, it's a screen
problem.

Prolly the video driver ... but we've also had this problem with a couple of
Toshibas in my infant school, traced to a memory card being jarred loose [1]
in it's holder. Turn power off, remove battery, undo memory card cover and
re-seat memory. Replace battery, power on and see if it helps.

Try an external monitor to see if it's the video card/memory or a possible
hardware fault.

[1] Supposed to be in clips, but possibly been assembled by monkeys and
always been a little loose. Once clipped back in properly they've never
failed again.