I removed all but 1 stick of RAM, leaving the last DIMM in slot B1. No change. I tried the same with the other two DIMMs. Same result. I tried to get into the BIOS by repeatedly pressing Delete at the frozen screen. Not only was I not getting into the BIOS but there were no beeps of protest. Bad keyboard? Bad USB port? Bad USB controller on the mobo? I unplugged all USB devices and unearthed a PS/2 keyboard. They system booted to the Windows prompt (Press Ctr+Alt+Del to begin) in 55 seconds.
This began the process of shutting down the computer, plugging in one USB device and restarting, shutting down, plugging in, etc., etc., tedium ad infinitum. The HP psc 1350 all-in-one causes the system to hang - but only if it's turned on. I have hated this {expletive deleted] piece of {expletive deleted] ever since I first hooked it up about 6 years ago and watched in awe as the installation took over 45 minutes. It had only taken 45 minutes to install the OS on the same system! But I digress . . .
The source of my woe was an hp printer. Powering it down before reboot cuts the system boot time from a horrendous 4 minutes to an acceptable 55 seconds.