Security - USB Antivirus, Scanners, Immunizers

Here is a list of possible software to guard your PC against an infected USB key flash drive

Panda USB Vaccine
Immunizes both the PC and the USB key.

Bit Defender USB Immunizer
"The USB Immunizer replaces any autorun file on the drive with a special one that can’t be deleted or modified by malware anymore. If you plan to to use your own autorun.inf file, then we’d recommend that you don’t immunize the drive, as you’ll lose your original file. Unfortunately, this is the only available approach to mitigate the effect of autorun malware.
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Gaijin USB Write Protector
Make the USB key write protected. Does not need to install software.

Autorun Disable

USB Guardian
Isolates the autorun.inf file and prevent access to it.
Parses the autorun.inf to look for other executables, then locks those executables too.
The user can run any other files which are not locked.

USB Defender Mbentefor Projects

USB Flash Security
Protects the contents of the USB key with a password.

TrendMicro USB Security
Not Free. $19.95

One way a malware can make use of USB to transfer malicious code, is to modify the autorun.inf found in the USB to automatically run malware. Knowing this, one way to solve this problem would be to make the autorun.inf unmodifiable.