It can still be recovered (hopefully). The system is actually quite robust as far as doorstop-recovery is concerned

- as long as the bootloader is still intact - and I think it is pretty hard to kill the bootloader.
The secret is the PCTool.
You have to assign the PC a static IP (e.g., 192.168.1.3) in the Windows network settings (assuming you're using Windows XP - if not, then this will not help you).
1. Turn the router off.
2. Start the PCTool.
3. Turn on the router
4. Wait for about 2 seconds (you only have a 3-second window of opportunity here),
5. Click on "Retrieve/Assign IP Address" and hope it finds the IP address of 192.168.1.1.
If it doesn't you will need to repeat steps 1 to 5 several times until it does. Steps 4 and 5 would be straightforward if you have the correct serial console cable (you will need to open the router and attach it to the right place). Biro knows a lot more about serial cables than me
6. Once the PCTool has found the IP address correctly, select "flash" for media type, and "binary" for file type, and then "download" your "Firmware - Kernel/FS" to the router.
7. After this is successfully completed, change your Windows settings back from static IP address to automatic, and restart your router.
Some screenies below: