Booting from a VHD on a system configured for iSCSI boot result in a stop 7B if created from a generic VHD.

When trying to boot a system configured with iSCSI boot which has generic VHD deployed, the system my crash with a stop code 7B while booting.

The generic VHD fails iSCSI boot because the network driver is not configured as a boot critical driver in that system image

iSCSI boot is only enabled by running Windows Setup on a machine with a specific network driver that supports iSCSI. Windows Setup is able to detect the driver and make configuration updates required for iSCSI boot. The only method available to prepare an image for iSCSI boot is to do a reference install of Windows Server 2008 R2 on a machine that has iSCSI network driver. Verify the system boots properly from iSCSI. Then you would use sysprep /generalize on that image, and boot into WinPE to run imagex /capture of the system image. Use Imagex /apply of the iSCSI prepared .wim image to a VHD file, as described in the OPK/WAIK deployment guide. The image in this VHD file would be able to use iSCSI boot on machines that have the same network device as the reference machine.

You can download the WAIK/OPK user guide from the following location:

http://www.microsoft.com/downloads/details.aspx?familyid=993c567d-f12c-4676-917f-05d9de73ada4&displaylang=en