I have started a download using Icon Downloader for NT that doesn't look like it will ever finish. In my notification area, it has survived two reboots and the uninstallation of the app. How can I get rid of it?
Usually if you long press on the downloading item in download manager there's an option to delete it, thus stopping the download.
If this doesn't work you can clear the Download Manager's data.
Here press force stop, than clear data. Now reboot.
Apologies for resurrecting an old thread but I just had the same problem of needing to stop a download and solved the problem by activating Aeroplane Mode.
A less invasive solution and more easily reached in the UI - for anyone else ending up here from Google (like I did :-))