In 2007 to 2009 there was an amazing peace of software for windows xp (but it worked perfectly for windows 7 as well) that used to display all the services running on a computer, what it was for and if it was needed or not.
There are similar software packages, but what made this different was that it explained each service accurately and in great detail, and also told you if you could turn it on or off, and what the impact would be.
Example: Shared printer over a network, not needed if you do not print or share a printer over a network.
I have never found another app that accurately gives EVERY service, what it does and what the impact is if it is turned off. Would love if anyone can help with this.