If you’re like me, and you tried to upgrade your router firmware, but found that you get a checksum error, you may want to try an alternate version of the firmware. After all, any newer firmware is probably better than what you have, if you have the factory default.
If you happen to have a TrendNet TEW-731BR, I have some specifics on how do this. The newest version (1.03b01) appears to have a flaw that prevents the router from running it. It did not matter how many times I tried to download and extract it, it failed every time. If you have this same issue, you'll need to grab the version prior to that (1.02b05), released June 26, 2014. I found it at http://download.trendnet.com/TEW-731BR/firmware/ which is the repository for all the TrendNet firmware downloads.
I was able to upgrade my TEW-731BR (1.0R) router without any issues using the 1.02b05 firmware.
Note that if you have a TEW-731BR and the router itself it does not have GREENnet written on it, you may have the TEW-731BR (2.0R). This is a different router and has a different firmware, which you can get from the TrendNet site here: http://www.trendnet.com/support/supportdetail.asp?prod=235_TEW-731BR
Updating the firmware is quite painless, simply open up the firmware admin, go to tools->firmware. Click the browse button and select the .bin file of the firmware you downloaded and extracted, and then click Update. After the processing countdown, the new firmware will be loaded, with all of your previous settings preserved.