Multiple installations and saving space after the fact

I bought and installed P 4.0 on my new MacBook Pro, initially installing it on my son's ID. I soon found out that I could not access it in the Admin's (my) ID, or in the 3rd ID. I installed software and Parallels twice in both IDs. My son uses it for school. How do I benefit from a single installation now that it seems that I have screwed things up. I have a full Office suite installed, virus software, windows updates, alas, hours and hours of work, plus files and snapshots. Any way to move my son's work to a shared folder and use the applications from one source, deleting the others, and free up the hard disk? 150 MB is chewed up and basically gone. Thanks in advance. Joe jwoneilljr@comcast.net

 

Anyone have a suggestion?

Thanks in advance.