I believe HFS+ is a closed specification, just like NTFS. Linux has beta write support for NTFS, so it's possible that somebody will port it to OS X once it becomes stable.
Until then, you should probably share data using a Fat32-formatted disk.
im dual booting windows on my mac, and i wanna be able to read and write NTFS from my osx OR read and write HFS+ from windows xp, i've tried MacDrive but it doesnt seem to detect my mac partition....

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