Before you try to log in again, check that where you see the domain name, it isn't part of a drop down box which offers you more than just the one choice. You might find Local machine lets you in without a password.
I pressed F10, then my computer restarted. It asked for my password. when I put in what I thought it was (long time ago, so not sure) it said "domain Jan is not available" and I can't log on to my computer now. what do I do?