One rule of thumb that I use, is: "Is it absolutely, positively, 100% necessary to have running all the time?".
Or, is it something you could run from a desktop shortcut, just when you need it?
Or, is it nothing you want running at all? Might be!
Then when you've settled that question, how about those G'Zillion Services that run in the background, that you never see. ???
On XP I either shut down or put into Manual Mode, 24 different services, using a batch file that I wrote.
On Windows 7 that number almost doubles and on Windows 8.1......well, let me just say "It's MORE!".
Services take up ram memory and also require service from your CPU. (somewhat slowing down your PC)
A good reference for what services you need and which ones you don't is the "Black Viper" website.
Get rid of all the stuff you don't need running in the background and your computer will love you for it.
I've been doing that since the first release of Windows XP, many years ago.
Cheers mates!
TechnoMage