As Mike stated, Many many services, UAC, Windows backup, Tablet PC and components and Games in optional features, Activity Center, Parental Controls, Windows Defender, Windows Firewall, Internet connection sharing, remote connect, Windows Search, readyboost
Do not download updates, let me choose.
Many more i can't think of at the moment.
In services:
Problem Reports and Solutions Security Center
Smart card
Smart Card removal policySuoerfetch
Windows Media Player Netowrk Sharing
All Media Center items becauses my TV card no longr works with my dual-tuner DirectTV recorder
I do use System restore as I'm a software junkie and that has saved my life many times. It needs Volume Shadow Copy service to be enabled also.