I'm pretty sure the following is accurate, but not positive. Please let me know if it fails.
Step 1: Get a fresh install of Minecraft.
Step 2: Download Minecraft Nostalgia:
http://www.minecraftforum.net/topic/106402-tool-cyborgs-tools-mcnostalgia-104/.
Step 3: Install Nostalgia and use it to downgrade to 1.2.5.
Step 4: Download Minecraft Forge build 152.
Important: This is NOT the current version.Step 5: Add it to your Minecraft Jar. *
Step 6: Download Mystcraft 0.9.1.02 Forge. Note: There is both a Forge and non-Forge download. Be sure to grab the right one.
Step 7: Add it to your Minecraft Jar. *
Step 8: Delete Meta-INF from your jar.
Step 9: Run the game before proceeding.
Step 10: Ask one of us for the .zip file of the rest of the mods.
Step 11: Copy all of the files in the .zip to your mods folder in Minecraft (NOT the Jar).
Step 12: Connect. It should now work.
Note: Our server is unfortunately VERY unstable. If you're getting a server not found, it almost certainly crashed - an error in following the install directions will instead either crash the client or give an error message of some kind.
* - For those who have never modified their jar, here's how that works:
1. Open %appdata%, via start->run (XP) or the search box on your start menu (7).
2. In there, .minecraft is (obviously) your Minecraft directory, and in bin under that, you will see minecraft.jar.
3. To copy stuff in there and delete stuff from it, you will need something that can read and edit Jar files on the fly. WinRAR is the usual choice for this. (Works well, free.)
4. To copy stuff from a zip file to the jar, simply open both and WinRAR, then drag and drop.
