If I install a new HD with the intention of of installing Windows 8, how would I be able to boot to the OS of my choice? Dual-boot option needed.
When you Install Windows 8 it will detect W7 on the old drive and install a W8 style bootloader to choose your OS, this will load automatically at startup after W8 is successfully installed.
The W7 drive needs to be connected at the time W8 is installed, so be careful and choose the right drive to install W8 onto.
Some do not like the new W8 bootloader and want the old legacy W7 bootloader, which can be changed after install of W8 if you like.