Brain Hackers

Depending on the version of Windows that you are using, there are different updates that you must have installed to correctly disable the Autorun functionality:
To disable the Autorun functionality in Windows XP, in Windows Server 2003, or in Windows 2000, you must have security update 950582, update 967715, or update 953252 installed.



Simple way to disable autorun.inf :
Follow this link and download the msi file:

http://go.microsoft.com/?linkid=9741395

Fix it yourself-Manually disabling the autorun feature:
To disable Autorun yourself on operating systems that do not include Gpedit.msc, follow these steps:
Click Start, click Run, type regedit in the Open box, and then click OK.
Locate and then click the following entry in the registry:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\NoDrive

TypeAutorun
Right-click NoDriveTypeAutoRun, and then click Modify.
In the Value data box, type 0xFF to disable all types of drives. Or, to selectively disable specific drives, use a different value as described in the "How to selectively disable specific Autorun features" section.
Click OK, and then exit Registry Editor.
Restart the computer.

you can re-enable the autorun feature :
Follow this link:

http://go.microsoft.com/?linkid=9743275

Actually i get this information from here:

http://support.microsoft.com/kb/967715

if you want more information  or want to disable in vista, just visit the above link: