Doesn't your PC have a boot menu? Mine (with an MSI motherboard) use F11, my Dell netbook uses F12.
If I press that during boot it comes into the boot menu, presents me all disks (hard disk, CD/DVD, USB) and ask me where to boot from. If I don't press it, it boots from the normal c:-drive.
I used this when installing Linux on a spare partition on my second disk. Normally that PC boots from the c: that only contains Windows XP. If I press F11 I tell it to boot from the other disk, which only has Linux as bootable.
Much easier than going into the BIOS to disable and enable disks!
What's your opinion about Windows 8, by the way?