How do I tell my computer it belongs to someone else now?

Last year, someone donated an old Mac Powerbook G4 for my use at work (non-profit). I used it for over a year, with the donor's name showing as the system administrator and the little house that shows in the finder window showed the same name. That computer just died, and I purchased a new MacBook Pro and used Migration Assistant to transfer my files from the old, donated computer. And now my new computer has the same donor's name everywhere as the administrator and owner. How can I change that to reflect that it really is MY computer now, and have MY name and info on it?

Thanks!!

a church musician

Take a look here.

Thanks - I've done those two things, and restarted the computer, but the little house (showing "home" on the left side of the finder window still shows the name of the donor. The computer still sees itself as his. Any other ideas? My new operating system is OS X Lion. The screens don't always look the same, but I followed the same steps.

Church Musician

Why don't you just clean install Lion? Afterward, use your Time Machine backup to restore what you need. The problem you ran into is that you used the migration assistant to carry over everything from the G4. That method would have worked great if the G4 had been in your name to begin with.

Messing with the home folder and changing names usually results in creating more headaches. You really should do a clean install anyway to get the most from your new MBP.