I took the latest version of ESXi 3.5 U3, and applied it to the post, and it worked great.
Seems to take about 800 MB of space.
I then applied it to a HP DC7800P desktop, and it booted great!
Then I found that the built in network card did not detect, so I tossed in two 3com 3c905b cards, and boom!, network connectivity, ( althrough ESXi see’s them as disconnected), it tests fine.
I then went into configuration and storage adapters, and saw that it detected the ICH9 controller, but no drives.
I found that I had to format the drives to fat32, and then it saw the drive, and I formatted it it to a datastore and it works!
I would recommend this configuration for a cheap none supported test box.