Just a heads up, you can make most of these changes on a temporary basis before starting your game.
You can kill process and services
from the command line or better, make a batch file to do this, then simply run the batch file using elevated permissions.
Example of how to stop a service. The following would end the Search Indexer Service:
Net Stop SearchIndexer
Example of how to stop a process. The following would end the Windows Media Player:
Taskkill /im wmplayer.exe /f
Here's a link
to an article on the topic.
You can also temporarily set the game to run with Windows Aero turned off, when you exit the game it starts again. Simply right click the shortcut to run the game and select properties, from the compatibility tab, check Disable Visual Themes and Deskop Composition.
This way you are not making permanent changes to your system. Just adjusting it a bit when playing the game to get better performance.