Help completely lost 3com 11g firewall/router

Hi I hope someone can help with this cos its driving me crazy.

Untill a few days ago everything was working fine. I have a laptop connected through wireless and a desktop wired.

One morning I switch the laptop on and get unable to assign IP so I contact the person who installed the network some 12 months previous who was of the opinion it was working when he left so tough.

I tried through what knowledge I have of wired Lan to manually configure the IP Default Gateway and subnet mask and all seemed good except it couldnot resolve the dns.

Ive tried entering the dns manually but with no luck I still get unable to resolve.

I considered resetting the router and starting from fresh but I really have no idea how to do this, and also the person who set it up as well as not helping with this problem is refusing to pass on the router password.

Any help is greatfully appreciated as I have hardly any knowledge of wireless conections. If you need any more information please ask and I'll do my best to let you know.

Many thanks for any help you may be able to give