Minecraft 1.4.6 Force Update Problem

I just bought Minecraft and suddenly my whole Minecraft folder inside is gone; nothing except saves. I tried to Force Update but it said Not Downloaded. I downgraded to Snapshot 12w50a/12w50b, and I still get the error Not Downloaded. I installed LWJGL, but it's still not working. I'm using OS X 10.8.3.

Go to C:/Users//AppData/Roaming/.minecraft (You must enable hidden files before doing this.)

Cut the folders "saves", "screenshots", "stats", "texturepacks", "servers.dat", and options.txt".

Make a new folder, and paste all the cut folders/files into this new folder. (This is to backup your worlds/screenshots, etc)

Delete everything else. Download Minecraft.exe from www.minecraft.net and run it. Now go to your backup folder you made, and cut/paste those files/folders into C:/Users..../.minecraft

If something says "Do you want to merge these files?" Say yes. If something says "Do you want to overwrite/replace these files?" Say yes.

Hopefully, you will have copied your worlds/screenshots/etc, re-installed Minecraft, and put your worlds/screenshots/etc back into your Minecraft game.