Any VMD files built with any 3.3 version but saved in version 4.0 will be automatically converted to the new file format. Please also note the following:
Saving a 3.3 VMD in 4.0 and later will result in a larger VMD file size since it is not compressed.
All 3.3 files cannot be opened in version 3.2.
Saving a 3.3 VMD in 4.0 and later, and then re-opening it in 3.3 causes three fields to be automatically set to default: