Question : Problem: a previously fine cd-r has somehow become no longer high sierra or iso 9660 compliant

Here's some background. A while ago a burned an iso file to a HP 700 mb/80min CD-R. I don't remember if I used easy cd creator or nero to do so. And the computer recognized it and I did an upgrade to my OS from it to xp pro. Since then the computer has gone through several upgrades. Here's the list of them-
-128 megs of pc100 ram to 256 megs of pc133               (m/b switchable)
-12x8x32 cd-r/w to 16x12x40 cd-r/w
-16x dvdrom
-linksys fast ethernet 10/100 adapter
-WD 30gig hd to WD 40gig hd

the system is setup with 4 ide devices -
- primary channel hard drive master, cd-rw slave
- secondary channel 48x cdrom master, dvd slave
on an EPoX MP3V-5(b? don't remember) motherboard with the via chipset which has been flash updated to recognize the larger hard drives. the cd-rw firmware has been updated to work with windows xp.

Now here's where the problem started, the old h/d(30gig) failed so I got a new one. And after I fdisked into 2 partitions 10gig/30gig, formated c: (using a win 98 se startup floppy) I tried to do a clean install of off my cd-r. that's when I got the following error "CDR103: cdrom not high sierra or ISO 9660 format reading drive E:" when I choose fail and I got "fail on INT24". So I installed win98se. Now when I stick the cd-r in any cdrom drive, windows explorer sorta recognizes it. The name by the cd icon on "my copmuter" is " CD(E: )" when I single click it shows 581 mbytes used 0 free, double click and it opens but nothing shows up in explorer.

Any idea's????

Answer : Problem: a previously fine cd-r has somehow become no longer high sierra or iso 9660 compliant

It's just one CD-R that is doing this?  It sounds like the disc is history.  If that is the only one that reads erroneously then give up on it and trash it.