lol, common crixx.
Disabling services and apps that you don't need @ the moment can have a notable effect on your PCs performance.
ZoneAlarm, Anti Virus apps, Anti Spyware, Printer Monitoring, Torrents, Email and other p2p apps can altogether wtfpwn your PCs ram and cpu. Rendering an otherwise burly machine into a sloth.
I definitely see some value in being able to rapidly stop drop these and renable them after for some maximum performance. As and when needed.
My gaming rig runs lean. Very little start up apps.