If you don't care about the system database currently on there, then do as nameless says. Grab the SD file and load the current OS 4.9x files on it and reboot the system. It will default it and you will have the latest software plus a clean upload. Also, you can default it, by rebooting and waiting a few minutes (normally once the unicard lights normalize), then holding in the reset button and counting to 20. This will default everything except for the IP on the system.