The parts need to be on the HCL other then that you will be fine
Check out these links...
Hardware recommendations to build a cheap ESX server - http://www.vmweekly.com/articles/hardware_recommendations_to_build_cheap_esx_server/1/
White box/Home ESX system - http://www.vmware.com/community/thread.jspa?messageID=620124򗙜
ESX on non-supported hardware to learn with - http://www.vmware.com/community/thread.jspa?threadID=77560
Community supported hardware/software for Vmware Infrastructure - http://www.vmware.com/vmtn/resources/communitysupport/
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The links in this answer are mostly broken. Either it needs an update or should be removed. Thanks.
that post was made in 2007 - of course they are dead
I would suggest you just post a new question
This question is answered elsewhere in the community. But for anyone who found this posting and is trying to find the answer to the question, here is where I found some assistance:
Those sites provide some testimonials regarding various "unsupported" hardware that works with ESX.