Ever wonder why your hard disk spins for 10 minutes when you boot Vista? Basically, SuperFetch analyses your behaviour and pre fetch in memory the apps you run on a daily basis. Great for an office worker that boots in the morning then runs to the coffee machine but clearly not useful when you're on stage doing a demo, rebooting after a crash or some incident with Beta stuff.
Here's a great article on Tom's Hardware about SuperFetch and ReadyBoost:
http://www.tomshardware.com/2007/01/31/windows-vista-superfetch-and-readyboostanalyzed/index.html
Now, can you disable SuperFetch? Yes you can but there's no UI, you need to change a registry key. I found this article via Fernando Guerrero:
http://origamiproject.com/forums/thread/19843.aspx
Anyway I disabled SuperFetch entirely by changing..
HKLM\System\CurrentControlSet\Session Manager\Memory Management\PrefetchParameters\EnableSuperfetch
to 0 (from the default of 3).
If you can't find the key, just search for EnableSuperfetch in Regedit.