To play Call of Duty 3 on a modern PC, you must use emulation software with a legally obtained copy of the game: How to Play Call of Duty 3 on PC via Emulation
There is no official PC version of . Unlike other major titles in the franchise, Call of Duty 3 was released exclusively for consoles (PlayStation 2, PlayStation 3, Xbox, Xbox 360, and Wii) in 2006.
If you see websites offering a "free full version for PC," they are likely distributing unsafe files or malware, as a native PC port does not exist. Additionally, downloading illegal or pirated content violates the Call of Duty Security and Enforcement Policy and may lead to penalties.