I am using ADT 2006. I have drawn a project using walls, windows, door, etc. Is there a way to convert this 3D drawing to a 2D?
Thanks.

I believe you can use the same commands in ADT that one uses in  AutoCAD to achieve this, but Im not sure about the version. I used to use the command SOLPROF all the time, but since AutoCAD 2007 I use the command FLATSHOT.
 
In your version, you should be able to plot to a DXB, which will flatten the 3D. You have to set up a DXB printer in Tools/Options/Plotting first
 
Creating a Solid Profile will give better results. Command SOLPROF.
 
Look these up in your help and see if they are available to you.