Hello Ductmate,
An .ipj file is a project file that keeps tabs on the information in the Inventor Project that would have been started when the project was first started. The file by itself is useless. If Inventor no longer exists on anyones computer then you won't be able to do anything with it but it doesn't really matter. All it would have done is keep tabs on all the files and folders associated with "Project X". All the files for the project should still be on the computers, you just won't know which ones went to which project. Here's an example: If you have a ProjectX.ipj file, you would start Inventor and go to "Projects". In the window that opens you will have a project called ProjectX. When you open that project, all the folders associated with it will be right there as shortcuts so you don't have to browse through your pulldowns every time you want to open a file. If you were to open up the ipj file with wordpad you would see text with the paths to all the folders that were associated with Project X.
I hope I didn't over explain that. In short, they are not drawings. They are just ASCII text files.
Powerhound
Production Supervisor
Inventor 11
Mastercam X
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II