The Undo commands also undoes Zooms in AutoCAD LT 2000i. You can always undo a number of commands at one go by selecting the down arrow between the undo and redo icons.
Use the plot command and select the HP plotter that you want to use. Select Properties, then double-click on Graphics. Select the third option (Merge Control) and make sure the Lines Merge option is selected. You'll then be asked if you want to apply changes to the current plot only or save the...
I think what you are describing is AutoCAD Design Centre. It list all entities of the drawing and enables you to do what you describe i.e. inserting blocks from one drawing to another. This feature is in AutoCAD 2000 and AutoCAD LT 2000.
I don't think the Flatten Lisp routine works in AutoCAD 2000. The way I convert a 3-d drawing to 2-d is to use the move command. Select the object to convert and use the Move command. Move the object from 0,0,0 to 0,0,1e99. Use the Move command again, this time moving the objects from 0,0,1e99...
