Going along with what Psycho said, go to a run command and type msconfig.msc
Go to the services tab, check the box that says "Hide all Microsoft services" then scroll through and turn off anything unecessary. If you're not sure about it, do research or leave it alone.
Next go to the Startup tab. Anything you don't need in here, uncheck the box. This will help free up RAM space and also make you computer boot faster.
As a general rule, if you don't need it to run your computer safely, don't have it running. Setting services to run manually is a good idea. Have them run when you startup a program rather then all the time