These instructions cover uninstalling a module from DotNetNuke 05.06.03, but should be good for DotNetNuke 5 installs.
If you are having trouble with a module on a particular page and are unable to remove it from the page, uninstalling the module will remove the offending code from the page as well.
1. Login as host to your DotNetNuke site and select “Extensions” from the host menu.
2. Find your module in the extensions list (in this case “Widget World”) and click the “X” icon.
3. The uninstall package screen confirms what module you are attempting to uninstall. If this is correct click “Uninstall Package”.
4. Once the uninstall is done DotNetNuke reports the steps taken. Any errors will appear in red.
Provided there were no errors you’re all done. If there were errors you will likely need to delete each file and database component manually.