AFAIK, EPs
after Pets use the latest EP executable, but EPs
before Pets use the latest SP executable. FFS was released between OFB and Pets, and it used its own executable, superseding OFB one. So if you have only up to OFB, I think you'll need to use H&M executable.
To avoid Securom being planted,
NEVER run the original executable that came on CD, use NoCD instead. Securom won't be installed until you run the original exe for the first time.
If you already ran the H&M exe once, backup your downloads and neighborhood, uninstall H&M (you don't have to uninstall OFB), follow the stickied tutorial to remove Securom completely, and do fresh install of H&M. Get NoCD for H&M from
GameCopyWorld and copy it to your <Your H&M Game Directory>\TSBin folder.