Any free antivirus for installing it on USB Drive

[nrkazmi]

Is there any free anti-virus utility which can be installed on a USB Thumb Drive, so that if I am carrying some important files and I plug it into an infected computer somewhere, the anti-virus residing on my USB drive can automatically prevent infected viruses or trojans from getting copied to my thumb drive automatically.

[HAN]

None that are free to my knowledge. I have read that the paid Avast U3 version can run a real-time scanner. I question how effective it can be because the U3 platform takes a while to boot up. Damage could be done before the scanner is up and running.

You can manually scan a flash drive from a flash drive with ClamWin Portable http://portableapps.com/apps/utilities/clamwin_portable But IMO, it's not the best AV available.

It's too bad flash drives no longer offer a write block switch. Or at least none I've seen lately do. Some older PNY models had a slider on the side that could set the drive to read only.

If you must use your drive on potentially infected machines, your best bet is to have critical files on your drive backed up somewhere else and to scan your flash drive from a clean PC once in a while.