Windows Antivirus 2009 is a virus that masquerades itself as an official Windows antivirus solution. It "scans" your computer and tells you that your computer is infected. To remove these infections you MUST enter your credit card information. Of course, this is obviously a scam to obtain credit card information.
Please do not attempt to install this on a Windows PC. The application creates popups, puts links to websites on your desktop, uses a ton of memory and plays videos of itself scanning and finding infections on your computer. It can also be a hassle to remove.