the term your looking for is that your router was bricked (because thats about all the functionality it has right now) but the problem is that the only real directions, that i could find, on how to debrick a router are centered around the WRT54G and WRT54GS by linksys, my suggestion is that you attempt to contact the manufacturer of your router although it's out of warranty they may still be able to tell you how to debrick it. if that doesnt work i'd say look over some WRT54G debricking info and see if you can find any information that could help you.
after all of this WRT54G talk i do suggest that if your router is bricked and cannot be fixed that you go with one of linksys's WRT54G/S routers as if your willing to use "3rd Party" firmware you'll have some of the best features for the money, unless you compare it to a smoothwall...