Okay got it working, checked the Fallout 3 expansion(dlc) install on my 20g oem drive, and found where the .pirs files should go and the folder name. Very simply the folder Content/0000.../425307D5/00000002 contains the .pirs files, in my case the folder had been moved the first time I copied Content/... from my MS 20g drive over to my wd 1t but the folder name was corrupt I think, because when I made a new folder and named it 425307D5 the content miraculously appeared from nowhere in the folder with the correct tree. Dunno if the game scans the folder names for sure but it seems that way as I has the .pirs files all over the drive in various locals and the game wouldn't pick them up, or u knew that already didn't you'all?

Case closed.
ok, can you explain the whole process in understable way, please, as I can't understand a word from what you wrote just there but I'm very interested.