Follow these tips.
In the bottom right hand corner of your computer if you see lot of icons start up when you first start your computer, then this the major cause for the slowdown of your PC. Try to get rid of unwanted icons from there.
Press your Start Button (bottom left) and go to "run"
now type in: msconfig
now you will get a box that pops up and will tell you bunch of stuff dont mess with anything else other than what I tell you now.
Now go to your "startup" tab on the top right of the screen where it usually place and click it.
Now you will have a closed in box with bunch of filenames and addresses and more boxes with checks in them. Now if you do not like anything startin up when you start your computer up then you have disable those programs. But other than that uncheck every box and then hit apply and ok. Then window will close and ask you if you want to restart or wait till later to restart.
Either way when you shut it off and then turn it back on the settins will kick in. Here you are.......your PC will be more faster now.