Create a new folder on C:\ named 5660upd (it will look like this C:\5660upd\ when done properly) and place the unzipped 5660Update.exe file there along with the 2.3.0(7) Firmware file or 2.3.0(2) Firmware file (if you use this version rename 5660_2.3(2).img to 5660.img after you extract it).
Now double-click the 5660Update.exe file and if asked, enter the IP of the 5660 (the default is 10.0.0.1) to begin the first step of the Firmware update process. The actual transfer does not happen until the utility checks the Firmware and validates the file. After this process the "Download New Firmware" button is activated and you need to click it to actually transfer the Firmware to the 5660. Until you click it no changes are made to the 5660.
Your PC should be connected directly to the 5660 to update the Firmware and the phone line should be disconnected from the 5660. Once started transferring do not interrupt the process or power off the 5660 or the PC and if you have the process hang or fail you can safely start over, but make sure you set the 5660's Ethernet Mode to Half-Duplex and then after the update is successful you can return it to Full-Duplex Mode.
Note: This process will harmlessly fail on a small memory 5260/5660 Hybrid if it currently has any v2.2(x) Firmware installed as there is not enough room to install the 2.3.0(X) Firmwares. There is a fix available HERE that requires adding a Serial Port connection (soldering skills needed) to the 5260/5660. Real 5660s do not have this problem.
