I have not installed release 11 in a long time, however there should be
options in both applications before you pick the install button.
Uninstall mechanical desktop 2007, then relaunch the install and you
will be prompted for the configuration for mechanical desktop.
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Dennis Jeffrey, Autodesk Inventor Certified Expert
Autodesk Manufacturing Implementation Certified Expert.
Instructor/Author/Sr. App Engr. Tel. (260) 399-6615
http://teknigroup.com