Damm I was so close. Had an old CD of an earlier PClinuxOS, a bit too heavy for a lightweight PC so it sat idling on the spindle for a spell. But I used it to run Live USB creator. It took a couple of tries. And then I booted the laptop; I even had to switch to verbose when the e logo wouldn't budge on the splash animation.
No joy: losetup couldn't mount on the loopback device. Or something to that effect. Probably a bad burn, it said. It also said to try mediacheck but as I've mentioned, mediacheck told me I've got a good CD. Is there maybe a script somewhere so I can run it off the console and make mediacheck look at the stick instead?