When Windows 7 arrives Oct. 22, it will have AutoPlay disabled on USB devices. AutoPlay has been disabled in the Win7 beta version for some time, but Microsoft just posted information about disabling it in Windows XP and Vista.
Microsoft support page here.
The Conficker worm and other malware have the capability of infecting flash drives then spreading to other machines.
After disabling AutoPlay on the drives (it still operates on CD and DVD drives), users will be able to open a folder and browse the contents of the USB drives.