Backup !

[motrucker]

Great tip! Though unfortunately the Catweasel doesn't work with NDOS disks, so wouldn't help the OP to recover his copy of Rainbow Islands.

@Jonas
Technically downloading an ADF is illegal. Whether or not you consider it immoral in light of the fact that you actually own a copy of the original disk is up to you, and I hardly think you're going to get Taito knocking on your door.

--
moto

A lawyer that I use says that under U.S. Copyright laws, you can download a replacement file (hopefully not a cracked version however) and replace your broken version with the download. This is IF you have a legal copy of the program. Copyright laws are NOT the same over the whole world however. Check with your country's laws. They may differ.
I'm not a lawyer, but I wont argue with him. He has a great track record for being right.

[motrucker]

Is it possible that it dosen´t work with KS3.1 ?
Is there somwhere on the net u can check what KS games works with or not ?

This is very possible! I keep an A1000 here just for old games that were made for 1.2 and 1.3 OS.
There are different programs that may help - relokick and/or degrader may help.