Go to the task manager Window by pressing Control+alt+delete, then go to Processes tab, find the jfilemanager image name, click it then click the end process - this will stop the program and allow you to uninstall it!
How do I uninstall JFileManager? When I go to Control Panel to uninstall, it tells me I have to close it first. I don't have it opened. I can't even get in to it.