It is the primary version used for older, "classic" mods that may not work with the newer Complete Edition or patch 1.0.7.0/1.0.8.0.

If you are planning to run:

Warning: downloading and installing game files from unofficial sources can expose you to malware, violate publisher terms, or be illegal. The steps below assume you own a legitimate copy of Grand Theft Auto IV and are seeking the official 1.0.4.0 patch/update or to verify your install. Do not use pirated copies.

While newer versions (like 1.0.7.0 or the Complete Edition) exist, the 1.0.4.0 patch is favored for several reasons: Better Performance: