Download Autoruns from Microsoft:
Instruct it to hide all core operating system items (Options -> Hide Windows Entries):
Starting with the
Logon tab, decide which programs you want to start with Windows. There's only going to be 3 or 4 that you actually use; uncheck the rest.
Next visit the
Services tab, where you'll see all the services that you don't need.
Note: Don't "uncheck" services, but instead use use Computer Management to change their startup from Automatic to Manual
Note: You'll see other services by Microsoft. In step 1 you hid services that are part of the operating system. These are different from services not part of Windows: such as services written by Apple, nVidia, and Microsoft. If it's a core Windows service, you leave it alone. If it's a non-Windows service, it's fair game for manual startup.
Additionally, all real-time virus checking software kills performance of any computer. Turn off real-time scanning, file scanning, network scanning, proxying, e-mail proxying, etc. If you feel as though you engage in risky enough behavior to need a virus scanner: schedule a scan for when you're not using your computer.
Short version: Get rid of junk. Windows runs fine, 3rd party baggage slows it down.