While searching the HCL forum, for successfull installation for esxi3/4 on a HP xw4600. I noticed this post here.
My question to you is, is this mobo installed on your xw4600?
Super Micro C2SBA++0 Q33 + ICH9R (SATA mode)
8GB Kingston DDR2
4 x 400gb Hitachi Enterprise SATA II Hard Drives (VMs and ISO storage)
Patriot Xplorer XT Turbo USB flash drive (ESXi)
Antec 300 Case
Stock out of box BIOS.
VT, VT-d support enabled.
The only thing that isn't recognized is the ITE8212 IDE controller that I was going to plug a DVD drive into but thats really not a big deal. ISO's work well enough and I'll replace it with a SATA model later. I'm really migrating VM's off my vmware server 2.0/linux rig as ESXi is far mor stable.
Everything else works out of the box...