Locked up and locked out!

An outside company attempted to take one of the systems in my charge and hook it into the WAN, which is also a part of the WWW. In the attempt, they locked the system up. I can’t get in, and I’m assuming that they can’t either (at least that is what they stated). What is the most logical method to break into the system and recover what was there without loosing the programming? The system was running Win 98 SE prior, and the attempt was to link with Win NT WAN and the WWW.