I’m going to solve this only because it seems a very particular set of information was causing the problem. While I was concerned my recent changes were the main cause, it seems they really weren’t, potentially.

I’m only solving because the problem was relatively easy to correct for.

(using latest undionly.kkpxe - with 2 ‘k’ as my undionly.kpxe file since the original does not work in this system - keeps restarting machine)

Just tested tftp client frm Windows 7 in one of these HP dc7900p computers, and it worked.
After testing all this, it’s working.
Don’t ask me why or how… but it started working.
Thank you all for your support.