double click My Computer
Right click the drive you want to autorun, select properties and then the autoplay tab.
Now make sure the little dot is in "promt me each time to use an action"
If that dot is there allready, click on the "select an action to perform", click on apply and then close the box.
Now go back and then add the little dot in "promt me each time to use an action" and press apply
see if that helps