Maybe (and that is a BIG maybe) there is a recovery partition on the HD with either the files you need, or the ability to burn a CD.
Different manufacturers have different ways of accessing that partition, when it is there. Maybe some README file on the work partition? Maybe poking around in the BIOS might give a clue, or if you have a hot Linux CD, booting off that would let you see what partitions are on the HD.
Be careful you don’t just restore the installed XP back to the original state and lose all the fellow’s settings and files.
Do you know which DLLs are missing?
I don’t know if SFC would be able to recover those files for you. With no internet connection it would have to be somewhere on the HD to recover those.
If cleaning up malware took those DLLs off, any possibility they got archived in a quarantine folder? And, would System Restore help, or did the restore points get removed in the cleanup?
If any service packs have been installed, the DLLs on a CD might not be appropriate now — but on the other hand, uninstalling those service packs might be an answer.
Another thought on the possible hidden partition. If you bring up the Disk Manager, you should be able to see if there are any partitions not normally visible. If so, maybe you can get to them by simply (temporarily) assigning a drive letter.
One Gateway laptop I had here had such a partition, but the contents were encrypted so you could not directly access the files.