Greek does not display correctly in iTunes

Question

I am currently using Japanese as my primary language on OS 10.4.3, and I am having problems with it displaying Greek correctly.
I have many songs in iTunes that have Greek titles and artists that do not seem to display well. The same goes to Address Book and iCal. The letters are correct ones, but it is very untidy and hard to read - some letters are italicized and each letter is very wide (like Japanese characters). This is a problem considering that I use Japanese, English, and Greek with equal frequency, although I would prefer to have my menu in Japanese in case my family needs to use the computer. For some reason, my iPod's language is Japanese as well, but the Greek there displays perfectly (in Helvetica font).
When I set the primary language to English in System Preferences, the Greek displays beautifully (again, in Helvetica). I therefore suspect that this incorrect rendering is due to the default Greek font (or its lack thereof) when the OS is set to Japanese.
Does anybody know any solutions for this issue by any chance? Thank you very much in advance

Answer 1

Thank you, your suggestion led me from one thing to another, and I think I came to some kind of compromise.
You were absolutely right about TinkerTool, where you can change the system languages. However, for some reason TinkerTool disregarded the fact that I was using Japanese as my main language, and showed that my system font was Lucida Grande (instead of Hiragino). So I went to VersionTracker and found the haxie Silk, which enables font substition, and it worked! I could allow only iTunes to show everything in Lucida Grande.
But then, being dissatisfied that I had to use a haxie to make this work (instead of just changing the font altogether) I found (finally, duh) that one could "turn off a font" in FontBook - but the Hiragino font (Japanese system font) could not be turned off. Upon changing the system language to English and turning Hiragino off, I logged off, changed back the system font to Japanese and logged on again, at which point the applications that used Hiragino no longer opened. sigh
After this adventure, I decided that I'll either 1) suck it up and buy Silk (to register it after my free 15-day trial is up) or 2) remove the Japanese language option for iTunes and Address book.
Thank you very much for all your help!