1) i downloaded by internet (from PG site) the MEGA REALCOMBOS files onto my win7 PC. Then i installed those files onto my win 7 PC and it works.
2) then i saved the original MEGA REALCOMBOS files (as received from PG download onto my win7 PC) and loaded them onto one USB drive.
3) on my win XP PC i tried to install directly from USB drive; it did not work.
4) then i loaded the 3 files from the USB drive onto my winXP PC hard disk. I tried to install those files and it did not work.
5) i did that manipulation half a dozen times; unsuccessfully.
6) desesperately i did the same manipulation on a 3rd PC (also winXP based) and i get the same result.
7) although i checked and compared the files sizes and on all supports (PG site/ win7 PC/ USB drive/ win XP hard disks/ ...); the error message is systematically "file corrupted"

For me there is definitively a compatibility issue win7/XP.

Thank you for your help.

Daniel

note : all the rest works onto my winXP PCs (BIAB2011, realtracks shots and holds, pro real combos). THe issue comes only with MEGA REALCOMBOS.