Peter Provost just posted on Speeding Up Vista Boot Time:
When you have a computer with a recent model CPU, chances are it's a dual-core CPU. Both Intel & AMD have been producing dual core CPU's for a few years now. By default, Windows Vista will only use a single core during boot-up. You can easily change this from the System Configuration utility:
He then goes on to show how to do this (not sure if he pulled the instructions from somewhere else since it seems to be quoted, but there is no source linked). Anyhow, you can do the same thing in Windows Server 2008 (just follow his steps).
I just tried it on my laptop and while everything still worked, I can't really say if it was actually faster.