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 [email protected]

 

Anyone have a suggestion?

Thanks in advance.