Yeah i dont know too! Im so sad because this **** comes back every time i start minecraft. I tried to turn off the internet so it cant be downloadet but minecraft deletets the whole version

I'm sad to hear this problem but I hope I can help. Here it goes:
You're using Windows 7. I've done it before and it works perfectly fine so I'm sure I should be able to check. First of all, make sure your jar file, json file and folder are all called the same thing. They are also CaSe-SeNsItIvE so make sure that they are all in the same case. next make sure that you edited the json file correctly. Have you gone into your preffered text editor? Since you are using windows you should have a program called "notepad". Right click on the json file and click on open with. A message should pop up with a list of programs installed on your computer. Find notepad and select it. Inside notepad, click on edit and then replace. In the textbox called "Find" type in 1.6.2. (a: Don't type the dot on the end of 1.6.2 and b: instead put the folder you copied such as "1.7", "1.7.2 Etc.) In the message box "Replace" type in the name of your folder (So because mine was "Mods" I would type in Mods. Remember: It's case sensitive). Then click on replace all and there you go. You have finished that. I hope this works for you and best of luck.

Happy Minecrafting,
FlamingoLord

Moajng made it that way so that release 1.6.2 wouldn't be hacked and then changed using mods. I think they made it so you would have to make a new version which was yours so couldn't be used to hack into the public versions. That's how it works (i think xD)

Thx for subbing and np