Microsoft's Free Safety Scanner

Run this if you have Windows. It will keep you from a mess on your computer if it catches malware etc...

Microsoft Safety Scanner Do you think your PC has a virus? The Microsoft Safety Scanner is a free downloadable security tool that provides on-demand scanning and helps remove viruses, spyware, and other malicious software. It works with your existing antivirus software. Note:  The Microsoft Safety Scanner expires 10 days after being downloaded. To rerun a scan with the latest anti-malware definitions, download and run the Microsoft Safety Scanner again. The Microsoft Safety Scanner is not a replacement for using an antivirus software program that provides ongoing protection. For real-time protection that helps to guard your home or small business PCs against viruses, spyware, and other malicious software, download Microsoft Security Essentials.

http://www.microsoft.com/security/scanner/en-us/default.aspx