It's possible that the CD or DVD that you put in is damaged itself, and your drive is fine. Have you tried using the same CD's/DVD's in any other devices, such as a DVD player? If the disk also does not work for the other device, then something is probably wrong with the disk. If the disk does work in a different device, however, then something is wrong with your laptop's optical drive. Please reference the following link if this is the case. Dell Inspiron 1545 Troubleshooting

The most likely reason for this is that your laptop is not receiving proper ventilation while in use. Using your laptop for long periods of time without a cooling pad or external fan will normally cause it to overheat. There may be other less obvious problems that your laptop is experiencing, which can be found in the following link: Dell Inspiron 1545 Troubleshooting