Can't connect to wireless connection fro...

There are only two options for you to get online like this:

1. Use a cable to connect to the router. A network key is only used for wireless connections - cable connections are always allowed, unless MAC filtering is enabled.
2. Reset the router to factory defaults. This is the main support page for your router (firmware, manual etc.) The direct link to the manual is here.

!!!Resetting the router to factory defaults erases all settings you have done. But since no one knows the password, I don't see another way. I would definitely take this step - you have to do it sooner or later anyways. And then at least you know the password!
Have your username and password for your DSL connection ready - you will need that information to connect to your service provider.

The Reset button is on the rear panel of the router.
1. Press and hold the Default Reset button until the Test LED turns on (about 10 seconds).
2. Release the Default Reset button and wait for the router to reboot.

Once the router has finished rebooting, connect to the router by typing http://192.168.0.1 in the address field of your browser.When prompted, enter admin for the user name and password for the password, both in lower case letters.

Voila!

If you have any more questions, just come back here and leave a comment - I'm happy to help and thanks for your rating.