The easiest and safest method is to buy the game from official digital stores:
This is the origin of the "highly compressed" myth. Repack groups (like FitGirl, Dodi, ElAmigos, etc.) are communities that specialize in compressing game files to the absolute maximum for much smaller downloads. A repack of "Assassin's Creed II" will still be a few gigabytes in size, not megabytes. The most reliable way to find these is through trusted public trackers, but you should know:
Many compressed versions pre-patch the game to work better on older hardware. Steps to Safely Download and Install
Because the game is older, you do not need an expensive gaming rig. Most modern laptops with integrated graphics can run it perfectly. 2 GB minimum. Processor: Intel Core 2 Duo or AMD equivalent. Graphics Card: 256 MB DirectX 9.0-compliant card. Conclusion: Protect Your Device