Where should I start?

I'm an amateur programmer. I know a decent amount of PHP and a tidbit of JavaScript.

I'm looking to learn some C# at the moment. In fact, I'm hoping to make a specific program but the problem is I don't know where to start.

I want to make a very simple program. All it does is show a custom screen on startup of the computer and have an icon in the taskbar. The only thing I want it to do right now is to have a password prompt appear if the icon is right clicked or if the programs exe is activated.

I assure you I am not trying to get someone to do this for me or to have the answers handed to me on a silver platter. I just want to know how and where I would start learning this.

Thanks guys!