1) Every computer MUST have an anti virus. From my experience the best anti virus available right now is AVG. Not only is it the best,
its FREE. Download AVG Free Here (make sure you uninstal any other anti virus software's you might already have).
Visit AVG's official site here.

2) Spyware Removal Tools
Spyware is a general term used to describe software that performs certain behaviors such as advertising in forms of pop ups and other
anoying methods, collecting personal information, or changing the configuration of your computer, generally without appropriately
obtaining your consent first. Spyware is often associated with software that displays advertisements (called adware) or software
that tracks personal or sensitive information.

Some kinds of spyware make changes to your computer that can be annoying and can cause your computer slow down or crash.
These programs can change your Web browser's home page or search page, or add additional components to your browser
you don't need or want. These programs also make it very difficult for you to change your settings back to the way you originally
had them.

Click here to download Ad-Aware SE Personal Edition by Lava Soft

Read More about Sppyware Here

3) Zango SpyWare removal tool
The Zango Toolbar software monitors and tracks the web sites you visit and the information you enter into searches on the web.
It will then use this information to place ads that don't belong on pages you visit, and also to bypass pop-up blocking software
and open new browsers on your PC containing even more unwanted advertising. Download and read
about the removal tool here

4) Learn more about Spyware and viruses at Microsoft.com