DD-WRT is a popular open source router firmware package originally developed for the Belkin WRT54G. The package caught my attention as it allows a cheap old router to be reused as a client wireless bridge. The download page has an excellent utility for identifying which routers are compatible. To flash my router I needed to use TFTP. First I established an Ethernet connection with a static, not dynamic IP address, then I downloaded the Linksys GUI tftp client. There are some comments on the DD-WRT wiki about Windows 7 using CTCP, but I did not have this issue. Instead the challenge with a Belkin router is to initiate the file transfer immediately after the router starts responding after a power cycle. The other issue I discovered is that not all bin files listed as compatible actually are: some bin files successfully upload but then are ignored. My problem, however, was resolved by some detailed notes on the wiki which recommended dd-wrt.v24_generic-8184.bin for my hardware.
If the upload is successful the router responds for a few seconds while the upload is flashed, and then the connection is lost as the router restarts and DD-WRT defaults to 192.168.1.1 instead of 192.168.2.1. Reconfiguring the static IP address and browsing to the new default address revealed DD-WRT successfully loaded on my device.