[gPXE] Only register bios drive without booting

[Miller, Shao]

Andrey,

In regards to your Windows 7 that boots successfully from gPXE but hangs
while the Windows logo is showing:

Have you any firewalls enabled in the Windows 7 installation which might
be interfering with the iSCSI communications?

Are you SAN-booting the same computer that you used to install Windows 7
onto?  If not, Windows 7 does not know about the NIC that you are trying
to use for the SAN-boot.

- Shao Miller