My Second whitebox:

The Hardware
-- ASUS Motherboard M4A88T-M
-- AMD Phenom II X4 970 - 3.5GHz
-- 2 x 4 GB DDR3 RAM
-- 500 GB Seagate HDD

The Software
-- ESXi 5.0 Build 469512

Changes in BIOS
-- BIOS Version:2403
-- Secure VM mode - Enabled
-- C1E Support - Disabled
-- Serial Port - Disabled
-- Parallel Port - Disabled

Other BIOS settings left at default

I did not have to make any changes to the ESX iso or add any additional files. Worked like a charm.