Thank you VoGT for your interest.
I ask because a number of people seem to have this problem but I see no explanations. In my case the box is headed Rnaapp and reads This program has performed an illegal operation and will be shut down. I am running Windows 98SE and the message appears anytime usually when playing a simulation type game but even in the middle of defragmenting. When this first appeared 2 years ago I contacted Tiny Computers who recommended running the restore programe but 3 months later it was back. Some times you can get the programe back,other times it crashes. Regards to all.