In my experience a boot drive will always be the first boot drive chosen on a computer.
That is to say, adding a second drive that is also 'bootable' should have no affect on your computer, except it will be visible in My Computer.
Side-note: By default the new drive might not be recognized by My Computer. You'll have to right-click My Computer from the Start Menu, click 'Manage', go to Disk Management, and find your un-named drive. Right-click it and click 'Assign Drive Letter or Path'. Now it's accessible from My Computer.
Edited by Ryan 3000, 16 November 2010 - 06:32 PM.
No pessimist ever discovered the secrets of the stars, or sailed to an uncharted land.