I don't have the model Tablet PC you have, you it might be worth checking
the user's guide from Acer, if you don't have the book:
You should be able to program the Tablet Buttons in Control Panel/Tablet and
Pen Settings, on the Tablet Buttons tab, including to "none" for the action.
Microsoft Windows MVP/Tablet PC
Tablet Creations - http://www.yqcomputer.com/
Expert Zone - www.microsoft.com/windowsxp/expertzone