If you are concerned about your computer being infected with who knows what, consider looking into this free online service from Trend Micro. This Web based virus scanner has saved my bacon more times with client PCs than I like to admit. While it is certainly no substitute for a having good client-side protection, it does make a nice extra bit of insurance in a pinch.

Give your PC a health-check while you surf the Web!
HouseCall is a real-life demonstration of the power of the web-based technologies that Trend Micro is developing to make deployment and management of virus protection fast and easy.

An innovative tool for scanning & cleaning viruses and checking your system for other security issues, HouseCall is based on Java Technologie that allows to support almost every platform, for which Trend Micro builds Security Solutions.