Modern game assets are already compressed using high-efficiency algorithms (e.g., textures in JPEG/BC formats, audio in MP3/Ogg Vorbis). Lossless compression algorithms (like ZIP, RAR, or 7z) generally cannot compress already-compressed multimedia data significantly further. Even with extreme lossy recompression (degrading game quality significantly), reducing a 20 GB game to under 1 GB is virtually impossible without stripping the game of essential functionality, rendering it unplayable.
The Ghost in the RAR File
If you manage to find a legitimate highly compressed version (usually around 2 GB to 5 GB, rather than 573 MB), keep in mind: Battlefield 3 Highly Compressed Pc Games -573 Mb-.epub
If you want to play Battlefield 3 safely, it is frequently available at very low prices (often around during sales) on legitimate platforms: textures in JPEG/BC formats