I can vouch that this does in fact work, a from a company called Bamboo Solutions which built an installer that allows you to install WSS 3.0 SP1 on a Vista machine. I haven't tested every single aspect of MOSS 2007 or anything exhaustive, but the Admin tool does work, you can create sites normally, etc. so it seems to do the trick.
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If you are into this sort of thing, check it out.