Open Windows Explorer,
Right-Click your CD/DVD drive and select Properties
click the autoplay tab
The drop-down box shows just about every type disk that can be used,
select each one and then in Actions, click "Select an action to perform"
and the click "take no action"
Do this for each type disk until they are all set to No Action.
Here is another method:
Run the Registry Editor (REGEDIT.EXE).
Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Cdrom.
Double-click the Autorun value, and type 0 for its value. (If it's not there, create it by selecting Edit -> New -> DWORD Value, and typing "Autorun" for its name.)
You may have to log out and then log back in for this change to take effect.