|I don't know what this is but can clear up some misunderstanding.|
Files are not in the registry, only references to them (when appropriate).
I have no PcmFmt.dll in my XP Home so I doubt it is provided with Windows. I would not therefore expect to have any associated registry entries.
There are various possibilities. You might have a corrupt registry entry from a previous install which is causing confusion. Sometimes reported errors are not quite the truth (kinda best guess), which can be misleading.
The disk could be scratched or damaged.
I would do that googling suggested earlier and be as open minded as pos. Avoid any magic fixit programs or websites that say it is a virus. These are all scams. This is worth reading:
If I find anything useful I'll pop back.
Always pop back and let us know the outcome - thanks