If you're not seeing a vmhbaX device when you run lspci then ESXi is having a problem loadnig the driver for the ICH6 controller.   I would suggest adding another controller that has been tested and found to be working.

You'll have the build in controller which will have SATA / IDE

interfaces.  Would you have an Adaptec SCSI controller lying around?

You might want to try that or list the list of controllers that people

have tested here

http://www.vm-help.com/esx/esx3.5/Whiteboxes_SATA_Controllers_for_ESX_3.5_3i.htm#SATA

No you don't have to add a SCSI controller for this to work.   ESXi is fairly particular at what hardware it will work with.   If you want a safe ,bet you would get something for the I/O HCL as this represents hardware that VMware has tested with ESXi.   Once you're off that list it's a bit of gamble as to wether or not ESXi will work with your hardware.   In your case, it seams that the driver just don't like the ICH6 controller,  so you're left with adding another controller to the PC or going with another PC. 

Thus if you have an adaptec card around I would try that, likewise if you have a promise controller.   See the whitebox HCL listed I posted above for other ideas.   Without a controller that ESXi can both recognize and load a driver for,  you're not going to get ESXi running on this PC.   Although you could try copying ESXi to a USB flash drive and boot from that, assuming your PC supports booting for a USB flash drive.  But in that case,   you would still need to provide some sort of storage on your   network (NFS / iSCSI - and there are free options for that if you have another PC around).

Once you have successfully booted your ESXi server, use the management tool (downloaded by using a web browser to your server's IP) to make the setting permanent. It's under Advanced, Kernel, Options I think. Just uncheck the box for checkCPUIDLimit and reboot.

To get it to boot from the hard drive, press Shift-O  on the bootup screen (where the white bar goes across the bottom) and when it gives you a prompt for advanced settings, put in the nocheckCPUIDLimit and hit enter a couple times. Should boot up then, and you can download the tool.