Here is something pretty cool which I have known for quite some time but thought I guess I better share with the little world that is interested in what gets posted here:

http://www.nliteos.com/
1. Take an XP image. Hack at it and remove all the crap you don’t want from it. And let’s face it, XP comes with a tonne of crap that no one uses.
2. Add your legitimate XP key.
3. Set configuration.
4. Repack and burn image.
5. Now your version of XP is not only cut down but is pre-configured and has the key so you just pop the CD, which drive to install it to and the rest is magic.

http://www.vlite.net/
It also comes in Vista flavour. Since Vista is worse than XP for the amount of crap it is packed, even when it is gutted, it still is far too dense for an enjoyable experience. Unless of course you have an high-powered machine in which case you are wasting computing power on your OS.

http://laptopvideo2go.com/nvlite
Strange I know but there is an application which takes you NVidia drivers and repacks them for taking all the additional crap out like multi-languages, etc.

God, I hope it comes in Windows 7 flava flav. Especially if history is anything to go by.