Don't know about Protel, but Vutrax has a facility called top down modify that lets you keep the existing layout & presents you with the extra components unplaced outside the pcb outline.

Perhaps Protel has this facility too.

Your best bet may be to first open the file and then rename it as something else. Then delete what you do not wish to keep on both the existing board and the existing schematic. That can then be saved as a "core" for another different design variation.

This should work for both schematic and PCB. It is mainly a case of keeping track of component designators. If you screw up, it will print out the usual hundreds of error messages, but with care it can save a lot of time.

All the self checking features of Protel should keep you out of trouble.

I'm using dxp2004 doing RF layout and don't understand  what the problem you are having. I have never used the autorouter (RF is always too hand-crafted for that), just the ocassional right-mouse-click to get to the interactive router.

I just add the components to the schematic, while in the schematic select the "Design" menu "Update PCB Document such-n-such". Let Protel drop the components at the edge of the PCB, then drag and drop where wanted.

There are a lot of setup features in Protel I'm not familiar with. Maybe you've got some automatic update box checked somewhere.

Also, there is a Altium:Protel forum in the "Engineering Computer Programs" group of Eng-Tips.

Thanks all
sounds like it entirely doable