DVDRW Problem Reporting its contents

I am encountering a really strange thing.

I am using W98, and I wanted to check the files in three DVD data
disks I have inherited.

I mounted the first, went to Windows Explorer, and all the data files
were listed as expected.

But when I mounted the other two disks, Windows Explorer continued to
report the same files from the first disk. Closing and re-opening
Windows Explorer did no good. My Computer behaved the same way.

Of course I thought just maybe whoever made the disks might have blown
the task and mistakenly made three identical disks (groan!). However,
when I shut down and rebooted and remounted disk 2, Windows Explorer
reported disk 2's files correctly. It showed disk 2's files when I
mounted disk 3 though - just like before.

When I shut down and rebooted, and remounted disk 3, Windows Explorer
reported disk 3's files correctly.

Can anyone suggest what may be going on here?

Thanks