Part of your problem could be trying to run LT 2000 on Windows 7.
Re: driver. Try uninstalling the plotter and then reinstalling. Uninstall first. Turn off computer. Turn on plotter. Turn on computer. Reinstall driver. Do a test print when offered the opportunity during the plotter driver setup. Did it work? If yes, then open AutoCAD and do a quick test plot as well. If not...well...it might be time to move up to LT 2011.