老靴, if you wanna DIY a small XP installation

try nLite to customize one for yourself. You might need to experiment a few times to make sure you have everything you need and not much what you don't. Virtual PC can help on that.

Sorry, I won't put mine online as it would incur licence trouble to myself :)

As CutOne said, there are usually large spaces used by XP updates. But you can delete them afterward. So far I haven't any needs to roll back any. To be safe, you can wait a couple of weeks before you delete an update backup files.