[1.2.5] Game crash upon launch

[ChristopheBeaudoin]

I am relatively new to modding, and I've able to install mods with little to no difficulty on versions like 1.12.2 and 1.7.10. However, I have encountered a puzzling issue regarding 1.2.5.

I'll first state everything that I have done so far:
- I've downloaded the client for Forge 1.2.5

- I've deleted the META-INF file located inside the minecraft 1.2.5 jar file

- I've copied the contents of the Forge 1.2.5 client (along with ModLoader and ModLoaderMP) directly into the 1.2.5 jar with winRAR

- I've put the rar file for the mod I wish to use in the mods folder

 

When I open minecraft 1.2.5, the loading screen will stop at "unpacking .....9.0-natives-windows.jar" with 0MB remaining. The game will then crash upon launch.

 

If I run the game with META-INF not deleted, the game will stay at mojang logo indefinitely.
Note that I am able to play Minecraft 1.2.5 otherwise.

If you know how to fix this, please tell me. If I should go somewhere else to get help for this, please tell me as well. 

[Cadiboo]

1.2.5 is ancient. No one knows anything about it. If you want us to be able to help you and give you support, you need to be on a modern version of Mc.