http://download.cnet.com/DoubleCAD-XT/3640-18496_4-11080692.html?tag=uo;uo

If so, then I saw this review which may be helpful;
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"Useful program"

by bfjones56 on November 14, 2009

Pros: Has good compatibility with AutoCAD dwg files.

Cons: Crashes on one out of four computers I've installed it on.
Summary: I have a licensed copy of AutoCAD 2002 and was having to read more and more files from more recent versions of Autocad (it has zero backward/forward compatibility). Rather than spending $900 to update AutoCAD, I downloaded DoubleCAD just to convert files back to 2002. So far, it works fine for that. I haven't yet spent the time to learn the interface and actually use it for drawing, but it seems to work OK, maybe a little slower than AutoCAD. The free version requires that you register, upon which you are emailed a serial number and activation code, so you can't just pass a copy around, but that's a small price to pay for a program of this value. Some of the other reviewers seem to have got the file somewhere other than the DoubleCAD site and, yes, they would not have the serial number or activation code. You can run it without the activation code for 30 days.
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So it seems you can run it without activation for 30 days. Is there a Next button on that serial number installation window?

Mark