1. Uninstall Arduino using Control Panel --> Uninstall a program2. Open Regedit using Start --> regedit (Run command) --> Yes3. Press <F3>4. Enter 'arduino' in the text box and click 'Find next'5. RMC --> Delete whatever the search highlights6. Press <F3>7. Repeat from 5 until the search gives up8. Reboot PC9. Repeat from 2 to check10. Quit when nothing found
If anyone has anything to add, please do so.