Problems rebooting

Figment

In that case I think your next step has to be to get hold of a replacement graphics card (borrow one if you can to check the card is causing the problem)

It's quite possible the root cause is a corrupted driver for the graphics card, but you can't uninstall it easily without getting into Windows.

Another option may be a repair install from the original Windows installation DVD if you have one.

Another thought. What does the LED on the monitor do when the 'No Signal' message appears?

Make and model of PC, and version & edition of Windows (see label on side/rear of tower)?

Electra_King

The LED on the monitor turns orange/standby.

It was a 'built' tower so no make/manufacturer as such. It is running Windows XP.

I wonder if it is overheating? Though the fans are running.

Will see if I can borrow a graphics card.

Figment

OK so that tends to confirm that the graphics card is effectively switching off when the Windows drivers are being loaded. I doubt it's overheating as if that was the case it would fail at random, not always at the same point.

Do you have the original Windows disc?