japanese/chinese/korean correct coding

[posix]

so i want to reinstall xp soon.

with my current install, german xp pro sp2, asian characters are not displayed correctly.

on filenames and in txt editors, i get something like ÓñÖóɌg instead of 玉置成実.

i can fix the characters by just renaming the file and it works well. needless to say that's not the way it's supposed to be.

this happens mostly upon downloading files that have special characters in their filenames.

why is my system able to display them fine but inable to keep the correct naming when downloading?

also, in windows live messenger, say i choose to enter a nickname consisting of japanese characters. it will display for a little while, then change to something like ÓñÖóɌg.

why is that?

furthermore,

when i only own the german version of winxp pro, can i still enable multiple languages for it?

like, can it be done so it's switchable between either german, english or japanese?

thanks a lot in advance for info.