for a Linksys WRT54G router (v2.0)
- download the openvpn firmware version from http://www.dd-wrt.com/dd-wrtv2/down.php?path=downloads%2Fothers%2Feko%2FV24_TNG%2Fsvn13491-snow%2FVINT/
- set you static ip to 192.168.1.7 and connect directly to the router via ethernet cable, disconnect internet from the router.
- once connected, update the firmware with the one you just downloaded from the link above.
- once done, successfully, reboot.
- re-connect the internet cable.
- 99% of the time it will reboot, though there's a fine chance of bricking the router so if you can get one from a yardsale, cheaper that way.
- once booted, navigate browser to 192.168.1.1
- login, the username & password could be either root/root root/admin admin/admin admin/password root/password.