PD11 can probably use the old project files, there may some items in the older pds files that are not in the PD 11 program. Some Titles and Transitions are not the same.
If you do edit you old projects in PD11, you will not be able to open the PD11 project file in the older Powerdirector.
Newer Powerdirector's can open older project files but older Powerdirectors can not open projects made in new Powerdirector's.
PD11 will open PD 10 and below projects. Not the other way, PD 10 and older can not open PD 11 projects.
Carl312: Windows 10 64-bit 8 GB RAM,AMD Phenom II X4 965 3.4 GHz,ATI Radeon HD 5770 1GB,240GB SSD,two 1TB HDs.