Before you run a repair or reinstall, try running SFC /SCANNOW from the Start menu, you will need your Xp cd.
That command will scan and repair as necessary all Windows files.
Another thing to look at, are you using Easy cd creator? that's been known to boot-hang, there's a patch available.
As a last resort, open your case, unplug all cards, ram, and leads, blow out all the sockets, and reinsert your hardware making sure it is all firmly in place.