I connected my computer to a domain , but now when I start the computer the screen pops up and ask for username and password and then it shows the domain name.

Is this a Windows XP machine?

If so, either had it set up to not ask for the username and password, and Fast User switching.

Since the whole point of a domain is to be secure, this is no longer allowed.

Do you know the Administrator password of the local machine?

if so log in as Administrator and select the PC Name as the Domain.

Once you long in, right click on My Computer, and goto properties.
If there is no My Computer, then goto contol Panel, System.
goto Network Identification and change it from a Domain to a Workgroup.
THEN
goto Control Panel, User Accounts, ahd change the way users sign in.

That will bring up the familiar windows pick your user thingy that i hate.

Hope that helps

you dont need to enter user name and password for changing from a domian to workgroup if you dont have wokkgroup set up in your network. once you changed it to workgroup your domian should no longer shows on the log in screen.
If you did not have a password for your ITIS login try username   administrator    and no password

First priority is to get your access back to your computer.

I might be going over the previous, if so, I'm just trying to make sure you do miss anything.

I believe you are now no longer a member of the domain (you selected workgroup).  If you can access your computer with your normal username, set a password for that username ASAP.  Press ALT + CTRL + DEL, and use change password (2000/XP).

Then, rejoin the domain (it is good to have the user account on the domain active directory as well), and try logging into your computer from the drop down menu (using your username and the password you just created).

Check out how everything is working at that stage, and let us know of your concerns at that point (if you get there.)

Thanks, Ollie.

if you did not want to join in domain then no problem login through administrator (if administrator account not display, login safe mode with networking,login as a administrator and click on workgroup (right click my computer - properties - network identification - properties - click on workgroup and type workgroup - ok - ok
     after this your computer prompt for restart, do this.

    when your system boot next time domain name not display and you work as a workgroup.
         
                                 ABLE TO WORK LOCALLY AND DOMAIN BOTH
First important things is if you want to change configration of your system (like join domain or relieve from domain) you must have administrative rights.
     when you boot your system computer asked network password ( at that time you see carefully, in last box you have two option domain or log on locally) log on computer as a log on locally.
      some time xp did not display all the account when you boot through safe mode you see your account and administrator account log on as a administrator and see the local security policy of your computer.
    start - setting - control pannel - administrative tools - local security policy - user right assignment - (in right pane) right click on log on locally - security - add - in upper ( select your username ) - add - ok - ok - after this restart your computer.
     you are able to log on locally. ( also give your account to administrative right )
           

dheerendra
(Network Engineer)