Windows 7 is as lean as it can be without cutting into performance. All services not needed at startup are set on Manual Fast triggers.
Those of us who tried Vliting it during beta found that there is no performance to be gained back from cutting Auto services - it can only practically be trimmed down for size purposes (language and drivers
) for netbooks.
Ultimate will default to the same as Basic on low-spec hardware.
The best approach to doing what you want is improving your hardware and assuring you have the cleanest possible install with absolutely no tweaking or optimization beyond what the OS has to offer itself - 3rd party tweaks will always come back to bite you in Windows 7.