Create a custom keyboard

Hi, I would like to create a custom Russian keyboard layout for my new Windows 8 machine. What is the best way to go about this? Should I start from scratch or should I try and modify an existing one? Either way, I don't know the process for doing this. Could someone please point me in the right direction?

I had a russian layout on my old xp machine which I was happy with but cannot find another like it in the ones shown in control panel on my windows 8 machine. Is it possible to copy the layout from xp to my new windows 8?