Did some research and found this ClamWin Portable Antivirus that can be included/extracted/installed to your USB flash drive/disk... you can scan your USB flash drive/disk anywhere even the PC you plugged into. What makes this ClamWin Portable Antivirus stand-out is that it is FREE and updatable anytime. ClamWinPortable is a stand-alone program that can be saved to your USB flash/thumb drive without installing it to your PC also.
ClamWin Portable Additional Description: (from www.portableapps.com)
ClamWin Portable is the popular ClamWin antivirus packaged as a portable app, so you can take your antivirus with you to scan files on the go. You can place it on your USB flash drive, iPod, portable hard drive or a CD and use it on any computer, without leaving any personal information behind.
Features:
ClamWin is a Free Antivirus for Microsoft Windows. It provides a graphical user interface to the Clam AntiVirus engine. It features:
--- High detection rates for viruses and spyware --- Regular virus database updates. ClamAV team regularly updates virus databases to include a new virus/variant immediately after it appears --- Standalone Virus Scanner
Please note that ClamWin Free Antivirus does not include an on-access real-time scanner, that is, you need to manually scan a file in order to detect a virus or spyware. Also, ClamWin Portable has scheduled scans and updates disabled as they are not used in a portable scenario.
How to install ClamWin Portable on your Portable Drive:
Just download the portable package at the top or click HERE, then double-click it. Select the location or the portable drive/USB drive you wish to install to and click OK. A PortableClamWin directory will be created there and all the necessary files installed are inside it.
I tried it on my USB flash disk and it works great on any PC, i was able to update it as well. Launch the ClamWinPortable.exe inside the PortableClamWin folder then click the update button to have the latest updates and virus definition/library.
Scanned it with Bitdefender Total Security '09, Superantispyware Pro, Trojan Remover and Spyware Doctor with Anti-Virus... it's 100% clean, nice work ClamWin ^_^
I also added autorun features on my USB flash drive with ClamWin Portable Antivirus so I can scan immediately once my USB flash/thumb drive is connected to any PC. (See image below)