It depends on how you saved your projects. PDR project files (.pds) simply contain a set of instructions for PDR to follow such as what files, where they are, what to do with them, what effects to use etc.etc. If you have the instructions i.e. the .pds and not the files it won't work.
PDR has an option to "Pack Project" and if you used this then you have everything you need in one place and can work with just that once you have installed PDR16 (PDR15 won't 'understand' the PDR16 projects).
If you have the .pds
and all the assets (the video, images, audio files & any special tansitions etc.) then you can still open the project and PDR will first tell you, one by one about the assets it cannot find. In each case you can then 'tell' PDR where the assets are and once that is completed the project should work as before on the new computer.