Sandboxie

Get rid of unsolicited software (spyware, malware and the like) that you download.

Changes made to your list of Favorites or Bookmarks, hijacking of your preferred start page, new and unwanted icons on your desktop -- all these, and more can be screened out with this software. It is freeware. It works in tandem with your antivirus software.

When you run a program on your computer, data flows from the hard disk to the program via read operations. The data is then processed and displayed, and finally flows back from the progam to the hard disk via write operations.

Sandboxie changes the rules such that write operations do not make it back to your hard disk.

Download it here.