Run the source port executable. It will automatically look into the id1 folder to boot the game. Managing and Modding PAK Files
This indicates a corrupted download or an invalid file size. A healthy, retail pak0.pak is roughly 18 MB, and pak1.pak is roughly 34 MB. If your file sizes are drastically lower, re-download or re-verify your game files through Steam or GOG. Quake Pak Files Download
. While there are various ways to download them, the "review" of this process depends heavily on whether you are seeking the (free trial) version or the Full Registered Downloading Quake PAK Files Shareware version (PAK0.PAK) Run the source port executable