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#11
There is no downgrade path for Win7. Vista would use as much or more resources.
XP might run well on it. Do you have retail copy of XP, or did it possibly come with the machine in question so that we could help you reintsall it with that license?
If you upgrade your RAM to 1 or 2 gb you can probably run Win7 fine on it. Do you need to know how to go about this?