Can somebody help me? I want to support the girls and buy the song (and other digital only H!P releases as well). How can I do so? I don't have any Apple products, so I don't have iTunes (yet?) and I have no idea how this works. This is the least problem, I can read that on my own language, as for how it works, how much I must pay etc. But I read somewhere that sometimes songs aren't available outside of Japan. Is this true for H!P songs? Btw I'm in Europe, so I'm not sure if they can be downloaded here. (Sorry for being noob and I hope this is a right place to ask. )
I'm not sure how you can get iTunes without a Apple product but I heard it's possible. But I can answer your questions regarding the releases: All songs so far since they've started to release digital songs and such are available in Europe as well. You can also buy the non-digital singles, albums and MV there. Just some of the older stuff isn't available online. Probably because they miss some of the rights for that.
Anyway if you manage to download and install itunes you should be ready to buy songs.