Exe files have to follow a certain format, and not every piece of machine code forms valid instructions. Yours was broken. You'd probably want to take some source code and compile it, if you want to create an exe.
First of all nothing to ashamed of in what you have done. Let me tell you what exe file is first.
Any application(an exe) is a set of instructions which are in machine readable format. You will ask what does machine readable format mean? It means that whatever instructions or operations we have asked the exe to do are to communicate with your Operating System in order to have a perfect execution. It needs some place to first place itself which is known as Load memory area. So the Operating System has to be informed such an application has been loaded in so and so memory address please ensure proper execution.
In order to do all these we have few function calls that interact with the OS. So if you are not making an exe have those function calling mechanisms in order to let the OS know its location and what tasks it needs to it is called broken application means it is accessing some memory which is not known or registered by the OS.
So I think I could give u a brief Idea about what exe is. Now whose job it is to generate all these function calls. Do you think the Programmer writes all of it. As a matter of fact no. Programmer writes only the portion of the code that needs to carry out the task that the application is supposed to do. Then there is something called a compiler. It will then take care that all the necessary additional information (as discussed earlier) is added to the exe. Without those information the exe can't be formed. So you can now understand that Notepad cannot do such kind of operation. hence the error u faced.
Please feel free to discuss any more issues or topics you want to know. I would be very pleased to help u out.