“alert case previously opened” Dell

Hi,
I had a customer that had me install a cd-rw on their new dell computer. I never asked about warranties. After removing the case a message appears in dos that reads “Alert, Case previously removed. We called Dell and was told only authorized Dell techs could do this and that it would void the warranty. My customer is furious with me beacause they have a 3 yr warranty and feel I should have known not to open case. Does anyone know how to reset this. It is win2000 pro OS.
Thanks if you can save me, customer wants me to pay for warranty, a valuable lesson has been learned.

“Have A Safe Day and Look Both Ways”