Looks like your going to have to do a hard reset. I think you need to press and hold the reset button, although this my have been changed by the firmware.
This will loose *ALL* your settings but will reset the password.
My other thought, is to see if there is a telnet password cracker / brute force login program anywhere. It might take a while, so you'll have to decide if its worth doing or whether re-setting up the WLHDD would be quicker.
When you can gain access to the setup page you can find the firmware version in the system setup tab.
Ade