I'm running out of ideas. I've installed the drivers for the SATA controller, SATA driver, and the network card pulled directly from Dell.com for the Optiplex 760 and upon PXE (when loading drivers) the message says
"The operation completed successfully.
Microsoft DiskPart version 5.2.3790.1830
The disk you specified is not valid.
There is no disk selected.
'There is not an available hard disk, or the hard disk driver is not loaded. Please inject the proper hard drive controller drivers....' "
All drivers have been verified and are the correct drivers.