Each version of Vectorworks has its own file version. (i.e. any file made in 2008 will have a flag that shows this when attempting to open the file in another version of Vectorworks.)
The previous extension for these files was .MCD, As of Vectorworks 2008, the new file extension is .VWX.
Some older file formats are no longer readable by newer versions of Vectorworks regardless of backwards compatibility. Vectorworks 2012 back to Vectorworks 2009 can open 2008, 12, 11, 10, 9, 8 and MiniCAD 7 files. Vectorworks 2008 and 12 can open as far back as MiniCAD 8.
If you have a much older file from Blueprint or an early version of MiniCAD, you may not be able to open it with a modern copy of Vectorworks. If this is the case, contact technical support at firstname.lastname@example.org
Edited by JimW