Yet another way to check the OS name.

[Pc_Not_Mac]

now please tell me that where do i write this code. i mean just simply on form load event or somewhere else.

You can but I made a sub for the method.
Just call Full_Os_Name anytime you want to run it.
You only need to run it ones so keep it in the load event.
I personal avoid having any code inside the load event as it gets cultured with methods.