OK. I figured out how to get the extensions to associate with Windows Explorer when Inventor View 2013 is installed and you do not use Inventor 2013. Thanks to the other posts that I read and I was able to add on too. I have uploaded a word document detailing each step. You will have to manually set the extensions, but once done they held and I was able to open the files from my desktop from my shortcuts. I am using Windows XP but it should work on Windows 7. Use at your own risk but it is not hard.
Install Inventor View 2013 and SP1. I did keep Inventor View 2012 installed or reinstalled it.
For good measure, reboot your computer after each installation
Go to Control Panel>Folder Options>File Types.
Find IDW to start with and highlight it then click on Advance.
Click on New and enter the following:
Action-Name it open
Application used to perform action (make sure it looks just like this with the quotation marks)
I just updated a newer computer with Windows 7 and all I had to do is go into Windows Explorer and right mouse click on the file and clicked on properties. On the first tab is has a button to change the program. I changed it to Inventor View 2013 and it worked fine. (You might have to browse to the proper exe file if this step does not work)
If you want to change the icons, then you will have to Google search and find the directions on how to change them in the registry.