I often leave the PC sometime just doing scans or overnight downloading of torrents etc with peer guardian on.

However yesterday morning when I came in, the monitor was blank and there was no power going to the keyboard or mouse. Yet the PC was on and the modem showed it had access to the internet.

After switching the monitor on and off, the monitor mentioned that it was not receiving any signal.

So I did a hard restart of the system, but with no results.

I don't have a spare monitor, but it does seem to be working (as indicated by the no signal message).

I'm thinking the graphics card may have died (its a 5 year old ATI x800) but that would not explain the mouse and keyboard situation (both USB types - oh and I tried switching them to different USB sockets but that didnt work either).

Any ideas?

Had exactly the same symptoms with a PC of mine in HK a few years ago after leaving it on doing some tasks overnight. Turned out the GPU fan wasn't working properly (bit gummed up), and coupled with the room not being air-conditioned overnight, I'd managed to "cook" the GPU which also caused some heat damage to the motherboard. Bit annoyed with myself as some online investigation afterwards showed that the GPU/fan in question (going back a few years - I can't remember the make/model) was overly susceptible to failure.

Hope your problem doesn't turn out as terminal as mine.