So I ran MCPatcher, patched ModLoader & Forge, then tried to run optifine, and it broke the game.

 

 

Launching C:\Documents and Settings\Widener\Application Data\.minecraft\bin\minecraft.jar

java -cp "C:\Documents and Settings\Widener\Application Data\.minecraft\bin/minecraft.jar;C:\Documents and Settings\Widener\Application Data\.minecraft\bin/lwjgl.jar;C:\Documents and Settings\Widener\Application Data\.minecraft\bin/lwjgl_util.jar;C:\Documents and Settings\Widener\Application Data\.minecraft\bin/jinput.jar;" "-Djava.library.path=C:\Documents and Settings\Widener\Application Data\.minecraft\bin\natives" -Xmx768M -Xms512M net.minecraft.client.Minecraft

MCPatcherUtils initialized. Directory C:\Documents and Settings\Widener\Application Data\.minecraft\.

Exception in thread "main" java.lang.VerifyError: (class: cm, method: a signature: ()V) Incompatible argument to function

at pb.<clinit>(Block.java:94)

at qa.<init>(SourceFile:14)

at net.minecraft.client.Minecraft.<init>(Minecraft.java:232)

at hq.<init>(SourceFile:2073)

at net.minecraft.client.Minecraft.a(Minecraft.java:2380)

at net.minecraft.client.Minecraft.a(Minecraft.java:2367)

at net.minecraft.client.Minecraft.main(Minecraft.java:2431)

Do not use MCPatcher.

 

It 'can' work, but only if you know very well how the process works, so it is better just to not use it and follow the standard installation instructions.