[ubuntu] stuck in command prompt mode

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http://ubuntuforums.org – using ubuntu 10.04. I was trying to resolve a problem with nvidia card drivers and the last thing I did was to uninstall and reinstall x-server. Now when I login, I don't get the graphical interface but instead I get a full screen command prompt mode. I can't seem to get out of it. How do I get the normal ubuntu mode back? (Hardware)