The windows folder should be roughly 10gb from the start. Perhaps a little under.
I agree with darkheart, I have now been running my Vista machine since roughly April 07 with no slowdowns (still runs quicker than the fresh XP SP2 install on another partition that I barely use except for oldskool gaming)... wouldn't know what is causing it though. Only thing I can think of is that in my experience uninstalling certain antivirus apps can make a hell of a difference... I'm talking some of the most popular free ones... if you uninstall yours and notice a large speed up on start up and especially on shut down then maybe consider a different one. Only thing I can suggest...
I agree with darkheart, I have now been running my Vista machine since roughly April 07 with no slowdowns (still runs quicker than the fresh XP SP2 install on another partition that I barely use except for oldskool gaming)... wouldn't know what is causing it though. Only thing I can think of is that in my experience uninstalling certain antivirus apps can make a hell of a difference... I'm talking some of the most popular free ones... if you uninstall yours and notice a large speed up on start up and especially on shut down then maybe consider a different one. Only thing I can suggest...