If you are looking to play this classic, the v1.8-Repack is superior to an old retail copy because it eliminates the need to manually download and install multiple, often broken, patches. It provides a stable environment to enjoy one of the best cooperative tactical shooters ever made.
If you can find a legitimate copy and patch it to v1.8 manually, support the developers. But for those seeking the definitive, offline, DRM-free experience—complete with all DLC and community fixes—the v1.8 repack remains the gold standard. Tom Clancys Ghost Recon Future Soldier v1.8-Repack