Will the original XP install disc repair the SP2 system?
NO. But it will make a usable "original" XP system which can be updated to SP2. That's if nothing else is wrong with your computer.
Yes, because the repair isn't specific to the OS. It's only a way to access a utility that'll give you options with the OS. Running a chkdsk will ensure the major OS components are in line with the standard Windoze setup. /f will repair anything that's gone wonky.
XP repair option leaves your files intact. All repairs are not successful but if it is successful it will bring your XP system back to the original state. You will have to reinstall SP2.
If you are very concerned about your files I would get them onto another hard drive before using XP repair
With a Knoppix CD or a UBCD CD you would slam dunk be able to boot up your computer and if you are able to connect to a network (your Ethernet is functional) you can e-mail your important files to yourself