Have you installed the Orbit Downloader and realised its crap and annoying and want rid of it. (Google Chrome Users)
Run through the normal uninstall process from Programs and Features, then reboot.
Once you have rebooted and you next go to download a file you will notice that it would appear to be still installed.
So Open a new tab in chrome.
Type (chrome://plugins) into the address bar, find the orbit plugin and disable it.
For internet explorer i believe you can just delete the folder in the APPDATA folder in your profile, ask if you cannot find this.