There's not really a way to do a factory reset on that device. What you'll need to do is get that MXeditor software working and then download the 507s2 MXD file to your pc. Load ONLY that device into the editor and then download that to you MX-700. I have the 507s1 upstairs in my theater. I just picked up an MX-800 for the downstairs.
Let's try to approach the problem differently. Can you tell me/us what exactly happens when you try to synch the remote and your pc? Have you tried changing which COM port the software is using to communicate with the remote over? Are you using the correct cable to plug into the serial port on your pc and the remote on the other end? Do you have another pc that you could try?
Let us know. I've done this on at least 4 different pc's and they each had their own little quirk to get it working correctly. More often than not, it's either a cable issue or a COM port setting isssue.
