I havnt tried this but give it a go found it from another source:
In Windows XP, you can disable autoplay for the entire computer or just
one user account by doing the following:
Start ---> Run...
This is the group policies editor.
Click "Administrative Templates"
then find "Turn off Autoplay"
Doubleclick it and set it to "Enable"
You can choose to turn it off for CD Drives or All Drives from the