#1 - X: is the drive of the WinPE image that runs Windows setup, and X:\Sources is the location of the .WIM files and tools needed to install Windows.
#2 - diskpart isn't a magical utility - it will only see disks (and disk sizes) reported to it by the driver
, just like any other windows application. It can manipulate disks at a low level, yes, but it won't see something that the driver doesn't allow it to see (for any reason).
I would still reiterate what the folks above have said - do a secure wipe of the disk, and then partition it with a 3rd party utility. Make sure the boot.wim and install.wim files in your \Sources folder have had added to them any SATA or RAID drivers
needed to see the disks (if it doesn't have that driver already), and you may ultimately have to ask the computer vendor what settings need to be configured for a proper Windows 7 installation on that hardware.
mercury3, I think you'll find that your current approach isn't likely to get you much further assistance. You probably want to remind yourself people assist on this forum, like many others, of their own time and goodwill. If you want either of those afforded to you by someone else here, it would be best to lose the attitude.