|When you have a DVD "combo" burner drive - reads and burns both CDs and DVDs, or a CD burner / DVD rom drive that reads and burns CDs and only reads DVDs, it has at least two lasers and associated circuits. Sometimes after the drive has been used a lot, one of the lasers burns out or the circuits for one becomes wonky, but in that case, you would probably not be able to read DVDs in Windows. |
Sometimes a bootable CD or DVD is not detected properly while booting after the drive has been used a lot. Sometimes that's because the laser lens is dirty, sometimes it's because some circuit or switch no longer works properly. You could try cleaning the laser lens on the drive, by using a laser lens cleaning CD. If you don't have one, they are usually available where CDs and DVDs are sold, and even some "dollar" stores have them for a buck or two.
In that case of a dirty lens, why would abootable CD be detected okay but not a bootable DVD? Perhaps because the data on a DVD is stored much closer together on the disk than it is on a DVD.
If that doesn't help, the drive may be defective, and in that case you need to replace it.
If other regular bootable DVDs, not copies, are detected as bootable fine.....
If the DVD you are using is NOT a regular DVD, it's a copy of a Windows DVD, then if it is NOT on a DVD-R disk, it may NOT be detected properly as being bootable if it was made in a different burner drive.