How to Disable Useless Services That Cause a Slow Computer

Part 1 of 3:

Click Start menu and select Run to use the feature. It will show you a "Diagnostic Box". The command is Msconfig.
Click the OK button to access System Configuration Utility interface. On the top of the window, you should click the "Startup" tab to view the startup programs list.
Uncheck any items you don't want it to load during computer booting. It will take effect after rebooting. Use Task Manager in Windows 8.

Part 2 of 3:

Your computer runs fast when it was bought. Why it becomes slow? People are not aware that additional services are added to your computer when you install some third-party software. As the result, the CPU usage may reach to a high level and memory is taken away. Then your computer slows down and crashes a lot. That nothing frustrated than getting into the trouble of a slow computer,

Check the service immediately after installing a new software.
Open the System Configuration Utility (as described in part 1)
Select "Services" tab to disable all the items by unchecking the boxes. However, without suggestion, we always make mistake when doing that. Manually disabling service does more harm than good.
Use system optimization tool as a good choice for disabling services. WinMate is free and can definitely speed up your computer.