Whoops, I guess I should mention that the RAID on the HP Z620 is not a REAL hardware (but rather Software) RAID, so ESXi will not see any disks you have in a RAID setup. The HP Z620 uses the Intel C600 chipset and that is the RAID Driver I used to install Windows 2008 R2 on, but then I switched to VMware ESXi to test hosting capabilities, which is when I noticed this problem.
Basically you will have to set your disks to non-RAID and then ESXi works normally or do what I did and install an old LSI 3041E 4-Port SAS 3GB RAID NIC that you have lying around, because this is recognized by ESXi as it is a hardware RAID.
:smileycool:
I am now testing vCenter 5.1 and possibly vCloud soon with a small "cluster" of 3 HP Z620s... Cool stuff...
Oh, and I FINALLY got a hold of an HP Z800 so I will see if that works soon and I spotted an HP Z820 "down the hall" so I might try booting it just to see if it works also, hahahaha...