1. Click start then type %appdata% exactly how i wrote it

2. Go to .minecraft, bin

3. Go to the file that says minecraft, go to the one that is a JAR file and right click then open with WinRAR

4. Open up the Zip file of TooManyItems then copy all of the files into the minecraft JAR file

Now run minecraft and your done.
How it works:
Because TooManyItems is something you use in the game and the minecraft jar file is the game and all the stuff in it.
e.g if i delete everything in that file then minecraft won't work. And in that file it has a file called gui . That is you inventory and other stuff. When you copy the stuff from TooManyItems it gets forced into the gui file. But you don't have to copy it there and you won't see it in the gui file. Now bye bye i hope this helped you, so fav and please comment on what you think and also if it worked.