I want to know where the Metro applications (Mail, People, Messages, ...) executable file path is.
Also, how can I run Mail application when my PC starts?
There are some tricky ways to start these Windows 8 applications, you need to find out its special name and since you cannot launch them with their executable (it only can be run from within Modern UI environment) but this is one way to start some of them.
To launch the calendar application:
To launch the people application:
You can try them from the Win+R as it is launched using cmd.exe
Here a list of some of them I found:
Just look for their names in Windows registry:
If they contain their default value with data like the following:
Try with that name with the command shown above.
And just make a shortcut and place it inside Startup folder
Some of the application cannot be found there, so this is the only method I know for the moment.
[UPDATE] And since those ":" <~ seems like calling a URL and its value contains URL: you can just use its name to launch them.
Example: (try it with Win+R just write its name and hit enter)
I am sorry, I forgot about this post. This is the method I would use:
From what I have read, you can not add a Metro app to autostart because it is an executable - however, there is a program called ClassicShell that somehow integrates the Metro apps into the start button that ClassicShell provides. If you don't DL ClassicShell, I'll check in a bit to see if one of these apps can be set as a scheduled task - I am running memtest on my desktop right now, so I am not able to check.
You can easily create a shortcut to the metro app and then place that shortcut into the startup folder.
To have Skype (or any other app autorun when you turn on your computer) simply follow the instructions listed in order here: http://www.thefakegeek.com/2013/12/how-to-run-skype-on-startup-in-windows-8-and-8-1/