XP Repair Choices

1) If you need to just replace a file, boot the OS cd and choose R for recovery console. (or you can have that choice already if you had done a d:\i386\winnt32.exe /cmdcons per http://support.microsoft.com/kb/307654

2) Or you might want to Repair the existing Windows installation and re-use the existing folder. So At the initial question hit Enter, then an R to Repair.

3) Or you might want to delete the partition on the hard drive (if bad viruses and rootkits abound, you may want to wipe the disk first)... For the initial question, hit ENTER, then choose Install, then look to the bottom menu area and take DELETE Partition (taking the next few confirmations). Then let it create a new partition for the OS, but generally, chose the QUICK format