I just spent the better part of a week trying to get ESXi to run on a newly aquired (to me) xw8600 with 2 quad Xeons and 22Gb RAM. The only distro I found to work without throwing errors or randomly rebooting during install was the HP Custom v4.1 Update 2.
To save on internal resources and troubleshooting time since it would have taken 100's of cd-r to get where I am now I tried the installs from USB drive. After I was successful with the usb drive I then used diskpart to clean, format, assign the usb drive, now that's totally clean and bootable.
Then I have a VM on the VMWare Workstation for my regular desktop. I pointed the vCD Rom to the iso installer for 4.1U3 and selected the USB drive as my install location. So now the whole machine boots and runs from the ESXi USB.
I'm goint to be trying the upgrade path from there. Fingers crossed.
