I don't have an edition of Vista yet, but I'll try to help with what I can
If you built this computer
Ensure you have all latest drivers
Especially Video drivers, this can cause problems with Power schemes
Some drivers may still be buggy
Also, I assume this is a desktop computer
Check your options in Control panel, since you don't have a laptop try High performance scheme
Here's some more info
http://www.thegline.com/windows/2006/12/th...-windows-6.html