Thanks, guys. I went to look at it this afternoon. Although Belarc™ reports that each of the two DIMM slots has a 128MB memory module in it, this was an error. Only one 128MB DIMM was present. I ran that Memtest86 program, and it reported 112MB present. Switched in one of my 256MB modules, and then it reported 240MB. Ran it with both (384MB) and Memtest86 reported 368 present. So 214th has it - 16MB is being allocated to the onboard graphics functionality. This tallies with the fact that there is no dedicated VGA card !!!!
It's basically a PC for the kids, but Dad wants it to work properly so that they can run their games. He also wants it to run faster - slow as all hell at present, but it ran quite a bit faster with my memory module in it. But he doesn't want to spend a fortune. So I've recommended an extra 256MB of memory, and a cheapo 64Mb ATI Radeon 7500 DDR AGP graphics card.
Amazing that Packard-Bell could turn out a system with WXP and only 128MB of RAM and no dedicated vid card. Oh well, that's boxed systems for you.