Motherboard: Intel 915G with PCI Express (MB ID:F90M).
NIC: Broadcom® NetXtreme Gigabit Ethernet Adapter [BCM5751] (Compatible and detected during install).
Controller: Integrated 82801FB ICH6 , Serial ATA (Select AHCI Mode!)
Chipset: Intel 915G + ICH6
CPU Socket: Pentium 4 (Hyperthreading models to 3.4GHz). I used 3GHz.
BIOS / firmware versions: R01-E0 (March 2nd, 2006).
Are the onboard NIC / storage controller working: Yes.
Any changes required to enable ESX/ESXi to recognize hardware components: Yes (Enable Enhanced Mode for SATA HDD Controller in the BIOS).
Does the storage controller support RAID / battery backup for write cache: No.
Does the MB support Intel VT (vt-x) / AMD-V: No.
Does it support vt-d (directed I/O) / AMD IOMMU: Doubtful (too old).

Note 1: Enable Enhanced Mode for On-Chip Serial ATA in the BIOS (Select: Integrated Peripherals -> Onchip IDE Device). Used SATA HDD.
Note 2: 3GB limit on RAM.
Note 3: Onboard Graphics is a bonus (Enable it).
Note 4: Supports ESX 3.5 and ESX 3i Update 4 installations.

Scenario: Two Acer Veriton 5700GX machines with ESXi 3.0 installed were used in conjunction with VirtualCenter 2.5 (on XP Pro SP2) as a cluster. Another Acer Veriton 5700GX was used as an openfiler iSCSI target server (shared storage). Excellent for practicing VMware Infrastructure 3: Install and Configure Labs. Wouldn't consider this setup for a production environment (der). Added a few more NICs (IntelPros) to make things interesting (multiple networks). This is a cheap practice solution for those that want to learn VMware Infrastructure 3. I'll let you know if Vsphere works later (I'm betting - yes, but could be a 64 bit issue). My students do an ESX 3.5 install on these all the time. I also use this setup to demo virtualization to small businesses (using local storage).