Firefox would not start today

I rebooted XP today, it had been awhile and my memory usage was very high. When I tried to open Firefox, I got this error message dialog box: "The program must close to allow a previous installation attempt to complete. Please restart." I did a Google search, and found the solution. I had to delete this file and all was sell: C:\Program Files\Mozilla Firefox\xpicleanup.dat
I found the answer here, thankfully that was quick and I can move on to real work.