I have also been tasked with upgrading an Inventor Addin created for a 32bit XP to use for 64bit Windows 7 and Inventor 2013. I have converted the programs for VS2010 and the compiles Setup works fine for 32 bit, but not for the 64bit machines. The present Installer class in the program does use Registration Services which register the dll incorrectly for the 64 bit machines (this I have gleened from other posts), but I still do not understand how to modify the code to create a Setup which will use the 64bit framework regasm.
The Install Sub (Uninstall looks sim):
PublicOverridesSub Install(ByVal stateSaver As System.Collections.IDictionary)
Dim regSrv AsRegistrationServices = NewRegistrationServices()
Inventor 2013 can use registry based installation for 64 bit add-ins but you are far better off using the non-registry based installation. There are lots of posts and articles on how to convert a registry based install to the new style. A search here or on the web should get you pointed in the right direction.