said by jbob :

There was a hardware change between v1 and v2 for some bug I think. My BEFSR41 clearly shows ver. 2 by model no on the bottom. I had a V1 but got toasted by a lightening strike. They also changed the power supplies. I can't find my v1 now but I think it had a two pin connector in the back while my v2 has the standard single pin hole. If I'm not mistaken the power adapter was inline for v1 while the v2 is a brick. The V1 and V2 use the same firmware.
I do not have a v3 but it uses different firmware as does the v4 now as well.

To access the router you do need to use 192.168.1.1 unless it has been changed from the default. If you are not sure of what it is then press the reset button in for 30 seconds(long reset) to accomplish a hard reset of the router. You should then be able to access it using 192.168.1.1 with the password (admin).

I am not sure now but did the earlier SR41's include an option to upgrade the firmware via the web interface? If not you will need to use the TFTP program found on the Linksys web site.