I also know this post is kind of old, but, there are some reasons for example ppl like me who can't have a better machine for now... I tried Service Controller XP and it does just what I wanted.
Why third Party soft? because you can GROUP services in different configs for eample I need to work with video editing software until 2:00 am and don't need the intenet nor any of the services related to networking.
Why not TuneUp, TweakXP or other soft, because they do LOTS of things I can also do manually and they can't Store some of this sets of changes made to the system.
With Service Controller XP I can restore a set of services and store 4 "States" or config sets, and manage them as needed.
If anybody finds a soft that can manage Windows resources by giving you several sets that changes: Services, StartUp, MemReleaser, CaheEnhance, Load/Unload Background Proceses or "pause" them to free resources, and still can group all that task in "State Sets" ... please tell me. (Sorry about my english - Spanish is my 1st L) Thanks to all.