For Windows XP, 7 and 8, go to Start > search > write “msconfig”.
A window will appear. Click on the “services” tab.
You should notice many services that are not really needed, Skype, Firefox updater, Yahoo updater etc.
Just disable them.
Your PC will boot faster without them. Be sure not to uncheck any Microsoft service (always have the hide option checked).
Besides the “services” tab, switch to the “startup” tab and disable any program that you don’t want to auto-start when you start your PC. Programs like Skype, Steam, Spotify, Dropbox etc.
These actions are really important if you want your PC to boot faster.
Also, read this old article, How to optimize your PC to run better, in 7 steps.