Quote Originally Posted by harrygno
... YES, I do have several "copies" of the original Knoppix all of which are equally useless.

I Got the cd from a magazine (a freebie) and until today it ran OK, (now I'm getting messages about "clean the cd" yet it looks sparkling and I've given it a gentle dust.

The CD has three files on it:
1) looks like a readme and offers no useful advice.
2) is knoppic.iso (with lots of other numbers between)
3) is the same file reference as 2, but it's a short file (opens in Notepad, nothing useful) with md5 extension, ....
You're very very confused about something. A CD with an ISO file on it will never boot into Knoppix. There is simply no way that such a CD "until today ... ran OK"

There is lots of information on this site for making a bootable CD, none of it will tell you that you can just boot a CD with the ISO on it. You might, after you figure out why you say that cd used to work, read the downloading faq found by clicking on the documntation link at the top of this page. And / or you can search the forums for the many many other times users have been talked through burning the disk properly. One good search term might be ISO, although burn and burning are also good choices.

You certainly can get error messages that a disk needs cleaned even if the disk shows no scatch. One source might be a dust build up on the CD drive's lense. But that doesn't explain a disc with an ISO file on it ever having booted and then stopping to boot.