DemonMaestro,  The first thing I would check is if the Embedded Sata Controller is enabled. If you go to the BIOS - Integrated Devices - Then check under Embedded SATA if it is set to OFF. If so, then change to ATA Mode. Table 2-4 on page 38 of this manual will show the selections. Let me know how it goes. 
I am trying to get the onboard sata to work.  I go into the bios and set the 4 sata slots to auto. hit save changes and reboot.Then it restarts and i go back into bios and it is set back to OFF. I am trying to add a WD Purple 1TB drive and a 40GB Intel SSD. Could updating the BIOS to 2.7 make it work?I have already wiped out the old OS so there is currently no OS on the drives.
Poweredge 1900 onboard SATA issues