just dragged out an old notebook with XP on it.

I imagine it is pretty much the same setup as your system. XP - SP3 with Japanese IME installed.

I've never had Chrome installed on this system before.
I downloaded google chrome 5.xx and loaded up some japanese pages and they worked right off.
I then uninstalled and installed the Japanese version - this also worked right off but with Japanese menus.

I am at a loss to explain why it wont work for you.
Possibly related to the bug I mentioned previously. If that is the case you will probably need to wait for that bug to be addressed.

I have a suspicion though that it may be more related to your language support install as I have now installed Chrome on three seperate operating systems (Opensuse, WinXP & Win7) & on each occassion it has just worked without me making any change whatsoever. Chrome doesn't actually need Japanese language support - it just needs Japanese fonts which for whatever reason it cannot see on your system.

One last thing you could try is . . .

 

Try installing some third party Japanese fonts.

or

reinstall Japanese Language support by going to
Control panel > Regional & language settings > uncheck "install files for East Asian languages" then hit apply (restart computer).
Then recheck that box and hit apply again to reinstall (& restart again).
Go to Details and make sure the Japanese keyboard installed is at least Microsoft IME 8.1

also worth a try

Change the default encoding to Shift_JIS and the default fonts to mspmincho and mspgothic within Chrome

or another

go to control panel > regional and language options > Advanced
and make sure "Code page Conversion tables" at least Roman, Japanese, Chinese & Korean are checked.
Could also try changing the Non Unicode language from the drop down box to Japanese.

Good luck - if these don't work try getting some activity on the bug report for Chrome