Cached credentials on a laptop that is part of a Windows 2000 domain

I've got a user who tried to logon to her laptop when she was at a hotel and it said it didn't recognize her username or password. She said she was trying to logon to the domain and not locally to the laptop and I pretty much believe her. When we just tried it connected to the network this morning everything worked fine, including taking the laptop off the network and trying the login. Now I've heard about cached credentials but don't know exactly how they work or if the cached time frame can be adjusted to where the logon credentials are only cached for a day or  week or whatever. Can someone tell me how I can look into the settings tht control cached credentials or is this soething that cannot be adjusted? In which case, I'd like an explanation of how it works or a link to an explanation please. Thanks.