4GB memory patcher
Generic Fix for any 32-bit executable
The generic fix (use on any 32-bit executable) is this tool: 4GB Patch, found at NT Core.
But to use it you have to know, and be able to point the tool to, the exact file involved.
[Similar tools linked below are designed for specific games, and they expect to find certain file(s) in certain location(s).]
Fix 2GB limit on memory usage for certain BethSoft 32-bit games
The 4GB Patcher by Daniel is a nifty little tool, that patches 32-bit (x86) executables (applications), to allow them to access 4GB (instead of only 2) of virtual memory on x64 platforms.
It will work for all 32-bit apps on 64-bit Windows systems, and is especially useful to improve performance of 32-bit games like Oblivion or Fallout 3.
WARNING: This may not work for all games or with Steam/OBSE/FOSE/NVSE. BACKUP YOUR EXECUTABLE BEFORE YOU TRY.
WARNING: Scan for viruses on any executable downloads, and always backup your Oblivion.exe and Oblivion.ini before trying patches of any kind.
Why do you need this tool?
These explanations of LAA (Large Address Aware) patching for Oblivion will satisfy your curiosity:
If you don't use OBSE, you can try the 3GB Enabler Patch for Oblivion by Chimera/hoihoi8.
Those of you who are also playing Fallout3, can take a look at a similar generic memory patcher (backup first!): FO3 RAM Boost
More Fallout 3 tweaks: Fallout 3 Tweak Guide