I don't know anything about Dells...but SATA slots that I have any familiarity with...are not earmarked for anything in particular.
If I have 4 SATA slots...I can attach the system partition/drive to any of those...select that drive as the first boot option in the BIOS...save the settings...and the system will boot from it.http://support.dell.com/support/edocs/syst...g.htm#wp1118793
That system supports a RAID setup, which is a special type of hard drive configuration where multiple hard drives are used.
I suspect that what you refer to...is part of the documentation for some type of RAID setup. That may require the slots to be used in some type of order.
You do not want to have a RAID set up on your system, there's a setting in the BIOS that controls that. I've provided the link above to your manual and you should find the appropriate information there about your BIOS options.
See Setting Your Computer to RAID-Enabled Mode
...and bear in mind that you do not want to enable a RAID.
Once that is done in the BIOS/Setup...save the changed settings and see if the system responds properly.