I recently switched from .5.2 to 6.2. I installed few mods, but when I launch the game, it automatically uninstalls all mods! I installed the mods by unzipping them into versions/1.6.2/1.6.2.jar, which if I understand correctly is replacing minecraft.jar for all purposes. In old client this behavior was done by the "force update" checkbox, but I can't see it on the new one.
Please, help
Since Minecraft 1.6, It is not recommended that you install mods directly into the jar file. You should be using a modloader like ForgeModLoader (http://www.minecraftforge.net/ (http://www.minecraftforge.net/)) and then using the mods folder.
If you still want to manually install mods, You need to create a new profile for it. There are plenty of tutorials for this already. Try this:
Minecraft: 1.6+ MOD INSTALL GUIDE! (With & Without Forge ModLoader) (http://www.youtube.com/watch?v=E7WfiKJr5h0#ws)
Thank you :)