Windows 7 has already been optimized as lean as it can be. Service edits that were used to gain back performance in XP and early Vista are no longer necessary as everything not needed at startup is already set to Manual and placed on fast triggers.
Beta testers learned quickly that turning off any of the network or security related services cause unintended consequences.
If you need better performance, visit the Advanced Tools page accessed by clicking your WEI score link at Computer>Properties. It will tell you at the top if you need to edit Graphics effects of sliding, fading, dragging intact, etc. to help with performance. Next Generate A System health Report which will clue you to weaknesses in hardware.
If you have a factory bloatware install, you can clean it up using these tips: HP laptop has used up all four primary partitions
Tweaking beyond normal system settings will almost always come back to bite you in Windows 7. This isn't XP or early Vista. This is the most lean, lightweight, perfectly optimized Windows yet.