windows – Can’t log into the computer

I just picked up a computer from the company that closed its doors couple of days ago. I was getting it cheap, so I couldn’t pass up the opportunity. It is a desktop with Windows 7 pro. It was used in the store, and was connected to company network/domain, with System Admin logon through logon servers. Now, I cannot get into the system. I don’t have Admin logon credentials, and even to change computer name, I have to login as Admin. When I try to do any system related activity, I just get a message that I cannot login because “Currently no logon servers are available to service logon requests”. What do I do !! I don’t want to have to format the hard drive and install Windows from scratch, and I don’t even know if this will work, and it would let me format the drive. Any suggestions! I’ll really appreciate.