At risk of getting rated down, the only ways to get a copy of the game in your situation are as follows:
1) Grab the disc back off your buddy,
2) Ask your buddy to make a copy of the disc and take that or your copy back (same as 1, but meh...)
3) Find an ISO (not going to list methods,) OR
4) Buy another copy of the game.
Estur Leone - Gysahl