First, let’s get the obvious out of the way:
A highly compressed repack refers to a version of the game that has been compressed to reduce its file size significantly. This process involves compressing the game's data, often using advanced algorithms, to fit the game into a smaller space. For GTA 4 on PS2, this meant that players could potentially download a version of the game that would fit on a single DVD or even a CD, depending on the game's original size and the efficiency of the compression.
GTA IV is notoriously unoptimized for PC, even on good hardware. To get a "compressed-like" low-storage experience:
Files found online with this label are almost exclusively based on Grand Theft Auto: San Andreas or malicious scams. The Truth About "GTA 4 on PS2"
cannot be compressed into a PS2-readable ISO because the architectures are entirely different. : These "repacks" are usually the modded San Andreas ISO mentioned above. They are small because the San Andreas
: The PlayStation 2 hardware lacks the CPU, RAM, and graphics capability to run GTA 4's advanced RAGE engine and physics. The Reality of "PS2 ISOs"
: Downloads promising a "highly compressed 500MB ISO" of a modern game are often deceptive, containing potentially harmful software or non-functional files. 3. Known "GTA IV" Style Mods for PS2