You can extract the key from regedit and save as *.reg file. You can recognize it, when you search for "flashpoint". But there are several "flashpoiont" in the registry. I have done it for not reinstalling OFP after the periodic Windows crash and reinstall.
Then make another installation of OFP, find the new key in regedit, which have replaced the old one.
Then in some way the same place you should manually create a same type registry key as the new one, but point it to the old instalation place of your OFP. Maybe it is enough to just make the instalation in same place, but start the two different files of OFP (not just shortcuts). And write the key manually in your newly created key.
Have not tested it, dont have two copies and keys. But hope this helps.