Log in to an account with Administrator rights or Administrator account itself.

Before you can disable Windows services, you must be logged in to an account with Administrator rights.  Alternately, you must actually log in as Administrator, which you can do if you know the Administrator account password.  On the assumption you know the Administrator account password, you can log in as Administrator by following these steps:

1. Log off from the currently running Windows account.    Click the "Start" button at the bottom left corner, and click on "Log of XXX". A small "Log Off Windows" box will open with the choice to "Switch User" or "Log Off"  Choose "Log Off" (the key icon button).

2. When you are presented with the "Welcome" screen, press the keyboard "Ctrl", "Alt" and "Delete" buttons AT THE SAME TIME, two times (TWICE).

3) You will be presented with the classic log on input box.  Type in "Administrator" for the user, and enter the administrator password, and proceed to log on as Administrator.

Disabling Specific Services

To actually disable specific Windows services, you...

1) Open the Control Panel and double click "Administrator Tools"

2) In the "Administrative Tools" Window, double click "Services"

3) In the "Services" window, double click the particular service you want to disable... in the following example, the "Alerter" service will be tweaked...

4) When the particular service properties window opens ("Alerter" Properties window in this example), drop down the "Startup type" and select "Disable", and finally, click on the "Apply" button at the bottom right corner of the properties window.

At this point, you have successfully disabled the service, but the service (if currently running) will not have been stopped.  You can optionally click on the "Stop" button to instantly stop the service, or you can leave it as it is (it will not start the next time you boot windows).  Note that some services cannot be instantly stopped in this way, but this is not an issue since the service will not start the next time you boot windows.

Click on the OK button to close the particular service's property window.  You can proceed to tweak other services and repeat the steps from Step #3 until you are done tweaking all the services that you want to disable.