I have a triple boot setup using 2 hard drives. On the main hard drive I have XP and Mandriva Linux. The Grub bootloader is installed on this drive, allowing me to choose between XP and Mandriva. On the second hard drive I have Windows 7. I installed Windows 7 on that drive while the main hard drive with XP and Mandriva was removed from the ThinkPad. Once Windows 7 was installed, I put the main hard drive back in, and put the Windows 7 drive in the Ultrabay 2nd hard drive adapter. At the IBM splash screen I press F12 to get the BIOS boot menu. From there I can choose which hard drive to boot.
If you have 2 hard drives, you can disable the drive that is not booted in Device Manager or in Disk Management. I disabled the Windows...