Have you got a backup of your data? Acronis or similar?
You should also have the serial number of your XP installation and a CD with XP Pro would be helpful.
You can make a boot disk but not a copy of XP Pro which is what you need.
Whilst the PC was shut down did you opened the PC up and check all connections to drives, motherboard, cards, etc?
If you decide to try this make certain you unplug from the mains first.
The fault may be other things but this is a hardware starting point.