Try right-clicking on the file and open with Notepad. In the header of the file it should tell you where the file came from (CAD System and version). At least this wil give you an idea of how much of a headache you are going to have. This is all barring that you don't have an install issue...
Can you use COSMOS Motion to get the impact forces then transfer this into COSMOSWorks? I am not exactly sure what you are looking for at impact, so forgive me if this sounds like I am simplifying the study.
Thanks,
Ryan C