Some patcher versions break the Steam overlay. Using the FNV 4GB Patcher (by RoyBatty) from Nexus Mods resolves this by preserving the original executable's import table.
The 4GB patch requires the Windows pagefile to be system-managed or at least 8 GB. A disabled or tiny pagefile will cause "out of memory" errors even with the patch, as Windows reserves commit charge from the pagefile. fnv 8gb patch
The 8GB patch modifies the game's executable to allow it to access up to 8GB of RAM, which can significantly improve performance, especially for users with large mod collections or high-resolution textures. The patch works by: Some patcher versions break the Steam overlay