The 1.3.1 patch officially removes the requirement to have the disc in the drive, which bypasses DRM issues common on newer Windows versions. Resolution & Widescreen Fix

Doom 3 does not natively support modern widescreen resolutions (e.g., 1080p). To fix this: Doom 3 on Windows 7 64-bit ? | Tom's Hardware Forum

Often fails to launch on Windows 7 64-bit without the v1.3.1 patch .

Generally runs "out of the box" as it is pre-patched, though some users report resolution issues.