As you might know, malware can take advantage of the Windows autorun feature to do their dirty deeds. For this reason, Microsoft decided to change the way that autorun works in Windows 7. 
Here’s a nice blog post by the Microsoft Security Research and Defense Team on the details of how they’ve changed the autorun feature to make sure that malware doesn’t leverage this feature in the future.
Check it out at:
http://blogs.technet.com/srd/archive/2009/04/28/autorun-changes-in-windows-7.aspx
HTH,
Tom
Thomas W Shinder, M.D., MCSE
Sr. Consultant / Technical Writer
Prowess Consulting www.prowessconsulting.com
PROWESS CONSULTING | Microsoft Forefront Security Specialist
Email: [email protected]
MVP – Forefront Edge Security (ISA/TMG/IAG)