Nice information you gave us
I didn't call protect.dll an engine but the critical place responsible for CD check. Furthermore, I suggested that it could be a good idea to crack Starforce that way because it requires the modification of single file only (protect.dll). And if you ask if Starforce engine was modified together with game exe/dlls, then no. Only protect.dll was modified. If you put xpandrally.bin (protect.dll) into original game -
it will be cracked .
Regards.