Login into Server 2003

So, I've been helping my dad's company out with their computer problems since they had to fire their whole IT department due to money problems.

They need me to access 4 servers because their IT department decided it would be cool to not write down any passwords.

I've made it into 2 of them, both because I found the old administrative passwords in a spreadsheet that was hidden REALLY well.

My problem with the other 2 is that, they are, I guess, trying to access the network, instead of the actual computer, to log in (I've never really used servers before so I don't know what it's called, but it will have like, a drop down box where you can choose which domain/network to access). The drop down only has the network... The only problem with that is that it doesn't actually exist anymore, so there is no way for them to log in.

My question is, is there anyway for me to change that (domain?) so I can log into the actual computer itself, and not the network? I cannot for the life of me figure out how without actually logging into the os I guess :v.

Oh, the IT guys also forgot to save the product key for Server 2003, so I can't really reinstall it.