Downloading a "Highly Compressed" version, often referred to as a "Repack" (like those from FitGirl or CorePack), means that the original game files have been algorithmically shrunk.
Before downloading, ensure your computer can handle the game. While Saints Row: The Third is well-optimized, it still requires decent hardware to run smoothly at high frame rates. Minimum System Requirements Windows XP / Vista / 7 Download Saints Row The Third Highly Compressed