AutoRun.Infi is the configuration file used by the Microsoft Windows machines to decide the action to be taken when a removal media like a USB or Audio / Video CD is inserted into the machine.
It surely saves some time for the user when without clicking or serching the file structure, he is able to get the desired action performed by the media. But many times, AutoRun feature has been seriously exploited by Malware to execute malware codes and infect your system.
The malware achieves this by copying a malicious executable in the drive and modifying the AUTORUN.INF file so that Windows opens the malicious file silently as soon as the drive is mounted. The most recent examples of this are the W32/Sality, W32/Virutas and also the W32/Conficker worm which, in addition to spreading via a vulnerability and network shares, also spreads via USB drives.
Security Experts suggest to disable this feature. After all your Internet Security is too important to be exchanged just to save a few clicks.
How to disable AutoRun Feature
If you search over Internet, you can find many instruction sets which will let you know the exact steps required to disable AutoRun feature of Windows. But if you prefer to use the ready-made solution and are scared to disturb your registry settings, then you can download and use the Panda USB Autorun Vaccine, which will do it in just one click for you.