You can try using SpyBot Search & Destroy(
http://www.safer-networking.org/), it comes up with a message asking for your permission to make registry change whenever you do things like install new programs. I think you'll find that Windows Defender (
http://www.microsoft.com/athome/secu...e/default.mspx) (Previously Windows Antispyware) does the same. Personally, I use both and they pretty much keep the machine clear of programs trying to do things they shouldn't.
Both Free too