This is how you fix the problem (this information is located in the Crash Troubleshooter on the XP Recovery CD):
If you can find the file, fdisk, run it outside of
Windows with the command, "fdisk /mbr". Or
you can type fixmbr or fixboot in the Recovery
Console which can be run from the WinXP CD (this is not XP Recovery CD, but the CD that you purchase from Microsoft (or the store) with Windows XP on it).
The XP Recovery CD does not run the Recovery Console.
The only other way to run the Recovery Console other than from the WinXP CD is by previously installing it on your computer from the WinXP CD (as described by Laverne in the post above).