By .ISEG do I assume you mean .IGES?

If you have solidworks then you will be able to export your file as an iges no problem.

If you don't have solidworks then chance are you would need to purchase a CAD translator for your CAD software, which won't be particularly cheap. It's not an open source file type so in theory you shouldn't be able to get a free one (though I'd imagine you can somewhere.)