Hardware Preparation

Lets start with the DC7900 and some background information from HP's official overview page. Some key features of this machine are...
1) It's almost "out-of-the-box" ready for VMWare except for a bug in the BIOS which might relate to this HP forum discussion "VMware / EM64T / VTd // HP DC7900".
2) The on-board RAID will not work with 3.5 apparently and possibly even 4.0.0 but I've not tested, will do at some point and report back about update 1.
3) ESX and EXi 4.0 compatibility notes can be found at www.vm-help.com and at ultimatewhitebox.com
4) Further discussions can be found on the VM-help forums, specifically HP DC7600 SFF (1),
HP DC7900 SFF (2),
VMWare ESX 3.5 on HP DC7900 and FAQ: Downloading the latest CommunityUnifiedDriverPack.

So, start by getting Vista installed on the box for a moment, if you're lucky it'll still be in it's post-install state just waiting for you to plug a user-name in and do some final configuration to it. As we've seen above you want the latest BIOS (or at least version 1.23) to make sure the VT-d will play nicely and it's also good practice, the Management Engine that comes as part of the Intel vPro also has a fairly important security fix so update that straight after doing the BIOS. The links above assume you have 32bit Vista Business installed by the way and when I first installed it didn't seem to recognise the network card so I had to use a USB stick to transfer the driver over from my Linux box. How on Earth can Windows not recognise a fairly standard Intel NIC?

With the BIOS and ME Firmware upgrades complete now is a good time to reboot the computer and check all of your BIOS seetings, specifically I'd suggest enabling Security -> System Security -> options 1 - 5 and 7 as well to "Enabled". This enabled VT-d (which you obviously need), some extra security features and the prompt for the Intel AMT Management Engine. With those enabled, exit the BIOS and hit "Ctrl-P" to gain access to the ME interface. Remember those extra vPro goodies I talked about earlier, this is where they come in, take a quick read of the first link to see if you want this and if so follow the instructions in the second link, the third link is for information later...

* Intel® Active Management Technology
* Hints on setting up the Intel ME BIOS Extension that apply equally well to the DC7900.
* Intel AMT Open-source Tools and Drivers on sourceforge.

Once you've set up the AMT you should be able to reach via a web browser from you're existing Linux machine and find something that looks like this...

...even when it's switched off! Great huh? Even better, later on when we've got CentOS installed I'll show you how to redirect the console so that you can access the machine during boot up from the boot loader onwards, this allows you to remotely power the machine on, enter an SELinux password and then login to the console via Serial Over LAN.