To troubleshoot an issue with a computer not playing DVDs, there are several steps to take:

1. Step 1: Check your hardware: Make sure you have a DVD drive for playing DVDs and that the drive is connected to the computer. Additionally, verify that the drive has power – look for an indicator light illuminating when a DVD is present.
2. Step 2: Check your software: You need a media-player software such as Windows Media Player or VLC. It must be installed correctly and updated to the latest version. Ensure that your software is able to play DVDs.
3. Step 3: Check your DVD’s condition: if the DVD is dusty or scratched, the drive may not be able to read it successfully. Make sure the DVD is as clean and scratch-free as possible.
4. Step 4: Check your DVD settings: Make sure your DVD playback setting is set to play discs automatically, and not to prompt you to choose an option.