You must legally obtain a PS2 BIOS file. You can dump this from your own PS2 console. Without a BIOS, the emulator cannot boot any game, including CoD 3.
Once you have downloaded your verified ISO, you’ll need an emulator to run it. -VERIFIED- Download Call Of Duty 3 Ps2 Iso Highly
Avoid "freeps2games" or "roms-download" clone sites. Many contain .EXE files disguised as ISOs, which are malware. You must legally obtain a PS2 BIOS file