While many games work perfectly, some in the 400-in-1 pack may be unstable, glitched, or bootleg versions.
Mesen (highly accurate, advanced features) or Nestopia UE (user-friendly, great compatibility). 400-in-1 Nes Rom Download
The bottom line: if you care about strict legality, your safest bet is to dump ROMs from cartridges you physically own. The 400-in-1 ROM, as a pirated multicart, falls entirely outside legal protection, but it remains a popular curiosity for retro enthusiasts. While many games work perfectly, some in the