Useful Programs:

http://www.ccleaner.com/download
http://www.tune-up.com/products/tuneu…
http://www.iobit.com/advancedwindowsc…

Services that can be disabled:

Application Experience
Computer Browser (If your computer is not connected to any network)
Desktop Window Manager Session Manager (If you don’t use Aero theme)
Diagnostic Policy Service
Distributed Link Tracking Client
IP Helper
Offline Files
Portable Device Enumerator Service
Print Spooler (If you don’t have Printer)
Protected Storage
Remote Registry (Always disable it for Security purposes)
Secondary Logon
Security Center
Server (If your computer is not connected to any network)
Tablet PC Input Service
TCP/IP NetBIOS Helper
Themes ( If you use Windows Classic theme)
Windows Error Reporting Service
Windows Media Center Service Launcher
Windows Search (If you don’t use Windows Search feature frequently)
Windows Time (If you don’t want to update system tray clock time using Internet)

Microsoft Windows 7/Vista Ultimate
Source: Youtube