Help!

My PC is playing up again. This is what the screen looks like when it loads; the colours are negative and out of focus and the screen is split with the RH side on the left and the LH side on the right. I've tried another monitor but that won't work as it is set to widescreen resolution, says it is 'out of range'. It looks in focus though.

What in earth could cause this? PC fault or monitor fault?

It happened before but went back to normal when I reconnected it - no such luck this time :-(

And back to work tomorrow* - boo. I have been ill the whole holiday and don't feel any benefit from the time off.

*actually back to work today. It's long after midnight.