I recently(yes, late to the party) updated to 1.7.4 on minecraft. Most of the mods I use, however, have not yet updated to that version, so I downgraded to 1.7.2 in order to use them. When I did, I ran into the same issue posted here.
I would have posted this on that same question, but having never used this site, I had to make an account, and therefor don't have the reputation I need to do so.
Anyway, I followed the steps that the answer shows, to copy and rename the 1.7.2 folder and all of it's contents. After doing that, I tested Minecraft using that version, and it worked. Unfortunately, however, as soon as I added in the mod files to the new versions .jar, any time I tried running minecraft from the launcher, it looks like it's going to run, and then the launcher just comes right back up and I never actually enter the game.
The only mods I've got are Modloader (found here: http://minecraft-mods.org/modloader/) and Timber! (found here: http://minecraft-mods.org/timber-mod/), and a Ovo's Rustic Redemption resource pack(which has been working fine on any version I use). Can anyone tell me where I'm going wrong and what to do to fix it?
Edit: Crash Log
Exception in thread "main" java.lang.VerifyError: (class: acf, method: getChunkGenerator signature: (Labv;Ljava/lang/String;)Ladn;) Wrong return type in function at abn.l(SourceFile:206) at kb.b(SourceFile:358) at azd.<init>(SourceFile:229) at net.minecraft.client.main.Main.main(SourceFile:84) Game ended with bad state (exit code 1) Deleting C:\Users\Owner\AppData\Roaming\.minecraft\versions\Modded 1.7.2\Modded 1.7.2-natives-50399431799411 Ignoring visibility rule and showing launcher due to a game crash Couldn't delete C:\Users\Owner\AppData\Roaming\.minecraft\versions\Modded 1.7.2\Modded 1.7.2-natives-50399431799411 - scheduling for deletion upon exit
Edit: Another update I tried using Forge, as was suggested in one of the comments. The tutorials for Forge past version 1.6.2 show just dropping the .zip for your mod into a "mods" folder in the .minecraft folder, but when I installed Forge as the tutorials showed, it didn't add a mods folder anywhere, and just creating a mods folder didn't get the mods to run. Minecraft is running with Forge, but lists nothing in the mods, likely because it doesn't know what folder to look for. I then thought maybe I could just add Forge to the Modded-1.7.2.jar, but I had no idea which files I would need to include for that to work, or if it could at all.