I want to add a Windows OS. Must it be on the boot drive?

I have all the components required to install Windows on a Mac Pro using VMware Fusion. Does the Windows OS have to be installed on the Mac's boot drive, or can it be on its own internal drive? All the descriptions I can find about installing Windows on a Mac leave a lot out and seem to assume that there is only one drive available and that the user knows all about the installation process. Do I need to format the Windows drive first? With what file system? Do I install the Windows OS first, then install VMware and hope that it finds the install? Who does what to whom and when? Any links about it?