Check out this post from Jason Hickey as he is spreading the word about the free stand alone and trusted DWG TrueConvert tool which handles R14 to 2007 and back DWG™ file conversions.
“I quite often hear grousing from customers (and non-customers) regarding the file format change in 2007. They all say that Autodesk is forcing them to upgrade by throwing in this file format change, and to that I say "Hogwash" (hey, there's a southern term for you!)
So, what if you're stuck on R14 and your consultant is on the bleeding edge of technology? Ask the consultant to save the file down (and get grousing from that consultant, and embarrass yourself in the process?) Not anymore! I'd look into a program called DWG TrueConvert. You can download it FOR FREE (I know my customers love that word...) from Autodesk.”
For more of this post please see (Beneath The Lines: What if I'm not on 2007? )