Assuming that you are running a windows based system, you could attempt the following.

1)Clean out your temporary files. Go to program, accessories, system tools and disk clean up(this is on Win XP).

2)Download a spy ware detector like adaware and run it to get rid of any spyware.

3)Update your virus scanner and run it.

4)Delete files and programs from your computer that you do not use.

5)Make sure you are running the latest version of your webbrowser.

6)Reboot your computer.

7)Defragment your hard drive.

What brand is your computer and what OS are you running? What are the specs? Go to My Computer Right click and go to properties. This will tell you what processor and how much memory your computer has. Let me know so I can be of further assistance