Having the same XP under Bootcamp and Parallels is the most flexible solution available (it's what I have and recommend), you can boot XP under Parallels and run it alongside OS X or, to take full advantage of your hardware, boot directly in Boot Camp. In fact, in terms of disk access it might be faster to run XP in Parallels from a Boot Camp partition than to use a virtual disk. I only see positive things about this setup, the only downside is just that it occupies more disk space than an expanding virtual disk (but the same as a fixed sized virtual disk).
Last edited: Dec 15, 2008