bio4.exe Collection file

1.1.0 - The latest version.
1.0.6 - One version back. Has next to no difference than 1.1.0 however.
1.0.6 (JP) - Latest Japanese version of the game. Has Amateur difficulty.
1.0.6 (Debug) - Allows you to activate the debug menu for RE4HUD.

Optionally, this includes bio4.exe pre-patched in 4GB and the permanent Corpse for all versions.

Install instructions:
Replace the bio4.exe in steamapps\common\Resident Evil 4\Bin32 with the one you wish to use.
Yes it's that simple.