The 8200 and 6200 versions of these computers are very similar, and seem to have the same BIOS, from their HP BIOS setup instructions HERE.
Note that the document states in the Storage Options section that the USDT versions do not have RAID. Is that the issue here.... do you have a USDT version and thus cannot see the RAID option in BIOS?
From work with the HP workstations I have found that some have the options of "RAID + AHCI" and IDE and some have the options of RAID, AHCI, and IDE. It turns out that the RAID + AHCI and the RAID options set during OS install get you the same exact thing.... those both result in the install of drivers for both RAID and AHCI. HP sends out the workstations with OS installed that way, and that also is the way that Intel recommends. I have found using whichever of those two is available to you in your BIOS will give highest compatibility and performance, even if I'll never use RAID on that workstation. I have occasionally had to switch back to IDE mode for some HDD and SSD firmware updates, etc., but always change BIOS back to RAID + AHCI. I have posted here about a SSD install that was done using IDE settings in BIOS, and when we switched things over to "RAID + AHCI" we about doubled the performance of the SSD. So, this stuff is worth paying attention to.
What you set BIOS to before the OS install results in different drivers being installed, and if you have things set to IDE during OS install you will get blue screen crash later if you change over to another setting. Big headache.... you might discover that your install is running slow because BIOS was set to IDE initially, and when you go to fix it you end up with a difficult fix for that little mistake.