How do I Make my Computer run faster for free

here may be two reasons why your PC is running slow.
1. You havn’t cleant up your PC for a long time.
2. You have got a virus or spyware on your PC.
I suggest you to run a virus test firstly with your virus scanner:(if you don’t have virus killer, you may try Avast OrKaspersky:
1. Firstly, update your virus scanner database
2. Then run the scanner and check whether you have virus on your PC.
When you find viruses, Kill them!
3.Then Restart your Computer.

Now you’ll find your PC is faster than before,

If not.
You may definetly need to clean up your PC.
Here is instructions about how to clean your PC: http://www.wikihow.com/Clean-Your-Computer
1. Download a nice PC cleaner from http://www.pc-registry-repair.cc
(System cleaner is a best choice)
2. Run the cleaner and clean up your PC.
3. Restart your PC

Source : Yahoo Answers