windows file locked or opened by another program

While trying to change a text file (krb5.conf), I continually received the following error message:

"please check if file is opened in another program"

In the end, the error was relate to my file permissions. Once I gave myself write permission, I could edit the file and save my changes.

Originally, the message lead me to believe that the file had been opened by another program; however, with the Windows 7 Resource Manager it was not possible to find such a program. This was the first time I had heard about the Resource Monitor. I was able to start it by first going to the Task Manager and pressing the "resourcemonitor" button (See below). I was very impressed.