Dual boot Win7 on external eSata drive with Precision M4700

Because virtualization doesn't support some HW devices I need, I would like to dual boot Win7 Pro/64 on an external (removable) HDD connected to the eSATA port of my Precision M4700.

eSata means optimal performances, but will the boot menu be happy with a removable disk, i.e. which will NOT be permanently connected (obviously I won't boot the OS on the removable disk if it is not connected) ?

And on the legal side, is it OK to use the OEM license of the OS that shipped with the system for this ?

As a side question, are the OS entries in a Win7 boot menu bound to a physical disk on a specific Sata port ? IOW, what happens if I move a HDD with a bootable partition/volume from the internal bay (port 0) to an external eSATA enclosure connected to the eSATA port (port 5) ? Is the eSATA port transparent to the Win7 boot loader ? Will the volumes and drive letters remain unchanged and appear seamlessly to the OS on it ?