Here are a couple of websites that deal with ESXi compatibility and motherboards/systems that aren't necessarily on the VMware HCL:
http://www.vm-help.com//esx40i/esx40_whitebox_HCL.php
If I were you, I would stick with Intel NICs only (staying away from the CT line of Intel NICs).
For your CPU, whatever you settle on make sure it has SLAT/RVI capability so you can nest ESXi 5.0 running as a VM with it's own VMs.
For reaching your Windows box, you'll need to install an iSCSI target software (such as Starwind iSCSI free version or Microsoft iSCSI free version) or use the Microsoft Services for Unix (NFS Server) software. ESX can't natively use Windows sharing for the location of VMs.
Datto