Instead of risky downloads, you can get stable, legal versions of the game (often including all DLC) on modern platforms. These versions are optimized for current hardware: PC (Steam/GOG): Fallout 3: Game of the Year Edition on Steam
Expect 35–50 FPS in interiors (Vault 101) and 25–35 FPS in the open wasteland. It is not perfect, but it is playable. fallout 3 rom
When players search for a "Fallout 3 ROM" for the PC, it is usually because they want to avoid the headache of getting the legitimate disc version to work on Windows 10 or 11. Instead of risky downloads, you can get stable,