What are unnecessary services in windows 7?

Well, You said it right. There are applications and services which are not necessary for a normal user.

Here I will suggest you to do the following and make your PC faster:
Managing Startup Application: Turn Off Unnecessary Startup Applications and Make your computer faster

• Start > Type "msconfig" in search box and hit Enter.


• You will get a new Dialog box "System Configuration"


• Click on "Startup" Tab.


• Uncheck all unnecessary application, which make your PC slower. You just want to run the "Antivirus" program and "Microsoft Windows", others can be turn off by unchecking it.


• After completing, Click on "Apply"


• Click on "Ok"

Now all unnecssary "Startup Programs are disabled". Sure it will speed up your PC.

If you don't want to get Windows Updates then just disable Windows Updates. Windows Updates may eat your internet data on background.
Disabling Windows Updates: How to disable Windows Updates and Save Internet Data Loss

• Start> Control Panel> System And Security.


• Below "Windows Update", Click on "Turn Automatic Updates on or off".


• Click on the Drop Down List below "Important Updates" and Choose "Never Check For Updates".


• Uncheck all other options.


• Click "Ok".

Hope this helps you. If have any doubts please feel free to ask.