woah woah woah before you go tearing away at the innards there are several options available to you (providing you have an xp install disc).
1.) Put the cd in the drive and boot to it, this may require you changing the boot order in your BIOS. Agree to the EULA then proceed to the installation portion of the disc. Usually you press F8 for the agreement and ENTER to proceed to the installation portion of the disc.
You will be trying for a repair install of xp, this is not the same as the recovery console, so don’t “press R to repair your installation using the Recovery Console”.
(you’ll see what I mean when you get there) Once at the installation screen of XP, there MAY be an option to “repair your installation of XP” or something along those lines.
I say MAY because if your installation is corrupt enough, the disc wont recognize it and wont give you the repair option. This repair installation is going to copy over all the core files for XP, the only things that may be lost are your My Documents folders. Nothing else should be touched.
Much better explanation and instructions here:
Try this before you go tearing up your machine, there are other options but this post is getting on to novel size.
Good luck