Start the computer hit F12 repeatedly until the bios set-up comes up.
Start-up tab > Primary Boot Sequence > Enter
<x> Exclude your Windows 8 hard drive from the boot order list > move the DVD drive to the top of the boot order list.
Esc out and move to the Exit tab > go down to OS Optimized defaults for Windows 8 > Enter and choose Disabled and hit Yes.
# Note: Have your Linux DVD in your DVD drive at this point
F10 Save Changes and Exit.
Install your Linux OS on your new separate hard drive. Update it, reboot it, do work on it, when ready to go back to Windows 8 restart the computer, hit F12 repeatedly until the bios set-up comes up.
On the Exit tab > Load Defaults > Yes [this should put your boot devises back in order] also > Optimized Defaults for Windows 8 Yes > F10 Save Changes and Exit.
Now every time you want to go back and forth you go into the bios remove the windows hard drive from the boot order and Disable the OS Optimized for Windows 8 to boot into Linux, and put it back and enable OS Optimized for Windows 8 to go back into Windows.
# Note: when going back to windows you may need to restart again F12 to bring up bios entrance window chooser but don't go into the bios, go down and select the windows boot loader to load windows and not the hard drive itself. otherwise you will end up with a no operating system error.
That is my new set-up until they come up with a better way to switch between them, it works for me.
# Note: while you are in your bios, it is always a good idea to set the password so if someone steals your PC then they just have parts.
Cr3D3