Up until support for the 32-bit version of Draftsight ended, I was running it in Ubuntu Linux.  I created 15 or 20 files.  The 64-bit version wouldn't run on my laptop because of the machine's graphics card capabilities.  I now have a new computer and have again installed Draftsight, this time in Windows 8.1. 

The problem is that more than half of my old files will not open in this new 64-bit Draftsight install (all of the most important files, of course). When I click on a .dwg filename to open it, the thumbnail shows up OK but I get this message: "This version of drawing file is not supported".

Why is this happening and is there a file converter I can put the files through to make them readable?

~Dave~