How to stop my text files open in cmd?

a few months ago i was having a go at scripting in batch script and vbs using notepad. when i went to open one of my files i must have gone and tried to open it with cmd by right clicking>open with>(because cmd wasn't listed) choose defult program>and finding the command shell thing. but i must have forgotten to untick "set as default program" so now all .txt files open in cmd but i cant just choose defult program and change it back because the choose defult program box is grayed out. i've tried the method were you go into the program the system has (sorry i have completely forgotten the name, hope this makes sence) and find the file extension and set it to open with a specific program but that didn't work. PLEASE HELP because this is very annoying now i have to right click on every .txt file and go on edit. btw im on windows 7.