Hi
I would recommend that you check with Dell for any known issues with that system and the Touchpak.
I looked at the Windows 7 Compatibility Center for the Touchpak and the Dell Duo does not appear on the list.
Windows 7 Compatibility for Touch:
Here is a link to the Dell Forums for your system category.
Dell Laptop General Hardware Forum
http://en.community.dell.com/support-forums/laptop/f/3518.aspx
Let us know what you find.
Regards