SQL 2000 installation

During the installation, I got a dialogue box message:

Files in use
The following file(s) are opened for exclusive access. Please shut down all other applications, then click Reentry.

There is a text box inside the dialogue box which suppose to show the file or application in use. However all I have is a blank text box instead.

Would anyone can help me on the issue. Or anyone can tell me how to find any hidden application is running in a computer.

Thanks
William