Did you by chance change the font or something used by your computer for things like filenames? Barring that, the only thing I can think of off the top of my head is some kind of OS corruption, and since you seem intent on not doing a repair install, I guess that just leaves you with living with the current situation indefinitely.
You can try the sfc /scannow command, though I'd not put a lot of faith in that working. It is, however, at least worth a try. Relatively quick, program is already on your computer, won't require a reinstall, but also kind of a last ditch, grasping at straws, kind of tactic.
Some what recently my computer no longer displays files in their native language as it has done for almost 10 years now.
For instance files in spanish will show squares. the only thing that appears to be working now are asian text.
I noticed it in itunes, as i have a lot of foreign music and itunes was also no longer displaying these characters correctly showing as boxes or incorrect signs in general everytime i would play the file... the weird thing is it displayed it normally until i click the file then it no longer displays it correctly after that.
I read around and the only solution i hear of is to repair the installation of windows xp but ill be damned if im going through all of that again.. i have tons of licenses and keys that are associated with programs that i have to go through so much trouble registering everything again just to repair fixing one problem.
i really cannot figure out what else it could be or how i could get around fixing all my languages in windows to at least display the file names correctly without repairing the whole installation.
I am not trying to have my UI changed into a differnet langue but only trying to get my windows xp to display all languages within files or exe's like it used to. Like i said this is very recent problem and for years i have never experienced this even installing easy asian language packs never affected it like this.. now all i can seem to display correctly is asian languages..
any help would be greatly appreciated.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic