Windows 7 - Win7 install to removeable drive

Currently I have Vista Ultimate (32-bit) and I want to keep that in place for a while. I have a limited amount of space in my machine so I have bought a HD caddy bay so that I can swap in a new hard disk from the front of the machine. I have bought two new drives and I have two caddies, so either one of those drives can be inserted. I don't want to hotswap, I am happy to power down to swap the caddy. Once the caddy is inserted it behaves as if it is plugged into sata05, (DVD is sata04) in other words, it is just another hard disk. (sata00 is the system drive with Vista, sata01 is a hard disk used to store data. 02 and 03 are not available.)

This is what I want to do. I want to clean install Windows 7 onto one of the removeable drives. I expect the install process to see that Vista is on the system drive and then set BCD to dual boot. If this happens, of course, it means that sometimes the Windows 7 caddy won't be inserted (the other caddy might have a ::cough:: linux distro), so I really just want the machine to default to Vista boot. I guess I can use bootrec to restore the dual boot options so that it just has Vista (and wipe any reference to Windows 7).

If I do this, how do I boot to Windows 7? When I start my Dell I can press F12 to get a menu of the devices to boot from, if I have the Windows 7 (or ::cough:: linux) caddy inserted, will I be able to use this menu to boot from that drive? If so, then I'll be happy.

Richard