Minecraft.jar?

Go into the folder and check if there is anything in there. If there is, it's probably stuff that your minecraft launcher uses to make the launcher and minecraft. If there is stuff in there, just left click and drag over everything, right click on one of the files, and then it should say somewhere on the little white box "compress x flies". Click that. It should open archiver and be compressing the files. Then once it is done, you will see a file that says "Archive.zip". Don't open that. Click on the text that is the Archive.zip name of the file. If you do this successfully, you should see the blue around it become a text box. Delete the text inside there, and type in "Launcher.jar" You need the .jar part, but you can mess around with the part before that. If this works, it should give you the gui for the launcher. This is what I did with my shiginima launcher, and it worked. If there isn't anything in the magic folder, then I think you should just get shiginima and do the whole process of doing the compressing and all that, but with the shiginima files.