I was able to boot ESXi 4.0 on a Dell Dimension 8400 workstation:

• Intel Pentium 4 CPU running at 3.0 GHz (processor ID 0F43)
• 800 MHz front-side bus
• 2 MB L2 Cache
• Hyperthreading (HT) capable
• Intel 64 (EM64T) supported
• Execute disable (XD) supported
• Dell BIOS version A09 (07-JULY-2006)
• Intel Application Accelerator RAID (SATA) in RAID autodetect/AHCI mode
• Broadcom NetXtreme 5750 gigabit Ethernet card
• 2.5 GB DDR2 SDRAM installed (2 512-MB sticks plus 2 1-GB sticks).
• This system does not support hardware virtualization.

I was pretty pleased to discover that this workstation, which my wife bought as a replacement for the old Windows 98 family computer, was 64-bit and HT capable. The onboard RAID controller appears to be working - the installer correctly detects the attached storage. I only have one hard drive installed in this machine, so I don't know the extent of RAID support under ESXi. The onboard NIC also appears to be working (at least according to esxcfg-info). ESXi reports that CPUID is limited via a BIOS setting, which I cannot locate in the current BIOS version (A09). I had to add the "nocheckCPUIDLimit" flag to the boot options in order to get ESXi running.

I can confirm that this box works with ESXi 3.5 u4 as well. NIC works, both SATA hard drives were detected (I too have not tested the raid portion).

I also had to add the nocheckCPUIDLimit flag in the install boot option, then use a Linux LiveCD to access /media/Hypervisor1 and vim the boot.cfg to automatically enable (disable?) the check.

upgrading it to ESXi 4 now - will post back the results of whether or not I need to re-enable the nocheckCPUIDLimit flag.

EDIT: Worked like a charm, and I didn't have to mess with any boot options.

I have an 8400 and am trying to run ESX4i on it.

I booted 3.5 just fine after entering the ignore CPUID directive.

When I boot 4.0 I get the Booting: MBI= error message, which apparently indicates unsupported hardware.

Any ideas what I am doing wrong? The only devices connected are:

ATI Radeon
SATA drive
CD drive
2GB RAM

Any help would be appreciated.

Does the MB have an onboard video card which could be using system memory?

No onboard video, it is a PEG card.

did you upgrade from 3.5 to 4, or do a clean install of 4? I did the upgrade route, FWIW, which worked flawlessly as noted above.

I didn't use a PCI-E video card though, I used an older PCI card (Radeon 9200).

No, it is a fresh install.

Actually, the video card is AGP not PCI-E.

When you get to the install error are you able to get to the vmkernel log (ALT+F12) or console (ALT+F1).

Neither of those keys work.

Are you trying to install ESXi or boot from a USB flash drive?