Set the files to read-only
Do this or look around for some mods. There are two or three you can use.
There's dispute of which method is better, however. It's really a lesser of two evils thing.
User Content Alpha can put more stress on your hard drive.
Badspot has advised against the read-only method.
Custom UI Mod causes GUI to take 16x longer to create.
GUI Replacer has some pretty big bugs as far as I know.
They'll all do their job to at least some extent, except GUI Replacer apparently just doesn't work properly anymore?