Wouldn't know where to start lol.
Pretty straightforward tbh, you should be presented with disk options when you use the Windows 7 installer. You can choose the drive you wish to install to, think it may be within an "advanced disk options" tab or similar, but it is certainly there.
I installed Win7 on my M8 on top of my alongside my Vista install and whilst keeping all my media files on the secondary partition using the options, when I transferred my M8's to my new laptop. It also left the original recovery partition from the old laptop intact funnily enough. You simply choose which partition you intend to install to.