It has been about 15 minutes and I am unable to connect. The router is just flashing the first progress light. At what point should I try to reboot the router? I saved the prior image but I have no way to reinstall it.
There is no other option than to restart it.
Restarted and it is gone.
I have a router from my ISP and was using the WNDR4700 (which has an internal HD) as a NAS. I have a hell of a mess.
There appears to be TFTP setup in the U-Boot enviroment. It seems you may have success creating a TFTP server, renaming the file to wndr4700_uImage.bin and placing it in the directory wndr4700. You will also need to configure your TFTP server to have the IP 192.168.1.7.
You should be able to boot the router into OpenWrt, and then use sysupgrade to flash it.