PC Doc Pro 3.5 is no doubt excellent, but pricey at $30 a seat!
"The registry software....examines your PC and produces a list of applications that are started when windows starts. By searching the internet to find out what each one does, I was able to uncheck a box beside each one that I don't want to run"
Mike Lin's Startup Control Panel does exactly that and costs exactly nothing.
http://www.mlin.net/StartupCPL.shtml
Of course PC Doc Pro has a Registry cleaner and various other goodies (but freeware equivalents aren't that hard to find on the Web).
Mac
Edited to add: Mike has a few other neat little tools available for free on his site - Clipomatic is one I use.