|If you are saying there is no reset jumper, simply remove power cable, remove button battery from MB, wait a number of seconds, and reinsert.|
If that does not get you on the right track, run Memtest to see if you have a memory problem (if yes, rerun with one stick at a time and replace as needed). If Memtest runs ok (even if ok with only one stick Memory) then your BIOS, MB, and RAM (hardware) is OK. If repairing windows still does not work, boot to a Linux Live CD to test keyboard there, and to save your files, since the next step the would be to format and reinstall XP. If Linux works, but you cannot access hard drive, it may be the problem. To be sure, run hard drive manufacturer's test utility from bootable CD.
You have to be a little bit crazy to keep you from going insane.
If all else fails, read instructions.