My original computer won't boot up so our uncle gave us an old work computer with a user name and password. I was trying to download iTunes on to it last night but it said I couldn't because of the network. So I Googled what to do and found an answer of changing from Workgroup to Domain. The computer then told me to restart so I did. Now the username and password won't work, and neither with Administrator with a blank password. What can I do?