take a look at this interesting thread: http://community.landesk.com/support/message/14232#14232
E5400 is not so much different to E6400, my drivers work for both, but I install fully unattended, no imaging... :-)
One thing you may check:
If diskpart is not able to see your drive in the device, it may be because thedrive access type is set to somethinglike AHCI mode in the BIOS. If that is the case, you can try to set the drive access to 'compatabile' mode and diskpart should be able to perform the required disk operations.
I have re-built my LANDesk PXE boot environment using WinPE 2.0 (WinPE Vista); this newer platform supports all teh newer drive acceess types so we don't have to go into the bios to adjust the access type.
Hope you get it!
I got the Dell Latitude E5400 to PXE boot finally by using the procedures for injecting drivers into the PXE image. The hard part was discovering the proper drivers. Thanks for the suggestions.