Panda USB Vaccine
Note: This review addresses v1.0 of the software.
Panda, an antivirus software company, has a new free Panda USB Vaccine available for download that can disable the Windows Autorun feature for an entire PC or a particular USB drive.
The Autorun feature in Windows can make it easier to install software--and it can also be exploited by malware like the Conficker worm, which co-opts the feature to spread itself. I've previously written about the risk, and turning off Autorun can be a good idea for better computer security.
When you run the tool, you can click a button to vaccinate your computer (disabling Autorun), and you can then click the button again to turn Autorun back on.
You can also connect a USB drive and choose to disable Autorun just for that drive. But note that it's a permanent step when done for a particular drive, and can't be reversed.
Note: This link takes you to the vendor's site, where you can download the latest version of the software.