Find the drivers online, download them on to a USB drive.
Download Linux (Ubuntu or Kubuntu, the latter being my preference).
Put in the disk, boot from the disk. Open the application "Dolphin" in Kubuntu. Find your C:\ drive, it should be listed on the left. Navigate to your drivers folder, should be in C:\Windows\System32\Drivers.
Copy the drivers from your USB drive in to the Drivers folder opened on your C drive. Shut down the computer, remove Linux disk.
Reboot in to XP. If you found the right drivers, then your keyboard and mouse should be working.
Granted, XP should have the drivers built in. Are you using a USB Keyboard and Mouse? That might be why they aren't recognized. Try finding a regular Keyboard and Mouse and see if those work. Remember, they have to be plugged in to make sure they work when you boot in to Windows.