Found this - might help
Explains how to enable also.
"Turn Off Autoplay For CDs
Click Start , click Run , type regedit in the Open box, and then press ENTER.
Locate and click the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CDRom
-To disable automatically running CD-ROMs, change the Autorun value to 0 (zero).
-To enable automatically running CD-ROMs, change the Autorun value to 1.
Restart your computer.
(NOTE : This method disables automatically running CD-ROMs.
If you want to disable automatically running CD-ROMs depending on the CD-ROM that you insert in the CD-ROM drive, you can press and hold down one of the SHIFT key while you insert the CD-ROM."