A No-CD crack for Project I.G.I. was essentially a modified executable file (a patched .exe). Skilled reverse engineers would disassemble the game's code, locate the routine that checked for the physical disc drive (the "Check for Disc" subroutine), and alter the machine code instructions. Typically, this involved changing a conditional jump instruction (JE/JNE—Jump if Equal/Not Equal) to an unconditional return, effectively tricking the program into believing the disc was present and valid, or simply bypassing the check entirely.
Older games poll mouse movements differently. If your camera spins wildly, go to your PC's Control Panel -> Mouse Properties -> Pointer Options, and untick "Enhance pointer precision". project igi no cd
Because the official game isn't sold digitally, you have a few community-supported options: A No-CD crack for Project I