I have been drawing around a bitmap image with the pen tool so as to export shapes to a laser cutter using dxf.
For some reason it has double lines when viewed in a cad programme.
However when I try it now it seems fine and is only drawing single lines!
Is there a setting that I might have changed perhaps?
Can I salvage my earlier drawing (making it export as single lines only) or do I have to start again?
Thanks

There are controls for the pen tool, I'd check those before drawing, especially if anyone else uses that computer with Inkscape.

Feel free to upload your problem svg file to a sharing service like dropbox and post the link so we can take a look.

Perhaps there was a path effect in effect? Make sure to not use any one of the 'shape' settings except 'none' when you draw your lines for cutting.

Can I salvage my earlier drawing (making it export as single lines only) or do I have to start again?

If we could see your SVG file, it would help us answer that question. (I don't think attachments are allowed on this board, so tylerdurden's suggestion would be the best way)

I know this is going to sound like a strange question, but I have seen it before. Are you sure the image you're tracing is a raster image? If it's already vector paths, that would explain why the cad program sees 2 paths - because there Are 2 paths!

If that's not it, is there any chance you clicked Path menu > Stroke to Path, either on purpose, or by mistake when you were aiming at Path menu > Object to Path? Or maybe did you use Path menu > Trace Bitmap?