If you get a message saying -+The program must close to allow a previous installation attempt to complete. Please restart+- when you start Firefox, it is because the xpicleanup.dat program file was not deleted.

Windows 7 and Vista

1. Select the Start Menu in the Windows Taskbar.
2. In the Search box, enter the following:
   %APPDATA%
3. Press Enter.
4. From the Application Data folder, navigate to Local\VirtualStore\Program Files\Mozilla Firefox.
5. Delete the file xpicleanup.dat.
6. Restart Firefox.

Windows XP

1. Click on the Start button and select Search to open the Search Results window.
2. On the left side of the Search Results window, click on the All files and folders link.
3. Click to expand the More advanced options list.
4. Put a check mark next to Search system folders, Search hidden files and folders, and Search subfolders.
5. In the All or part of the file name field, type xpicleanup.dat.
6. Click Search to begin the search.
7. If any results are returned, delete them.
8. Restart Firefox.