How old is the system? Does other DVD media work? I'm assuming you burned the ISOs to DVD-R discs...?
My first thought is that the drive does not support DVD, which would date the system as fairly old. If this is the case, you'll probably need to upgrade the optical drive (fairly inexpensive and a rather simple procedure).
If the system is newer (within the last 5 years), the drive would be DVD-capable. You can tell by looking at the drive tray front panel. It should be pretty obvious (look for the DVD logo). If it's capable, but having trouble, the drive itself may just need replacing. Same fix as if outdated. Just be sure you know the connection type (IDE vs SATA). Most drives now are SATA. Take out the old one and bring it with you to a local electronics or computer store if you're not sure.
Last thought is that you're using the same media for all the Linux burns. If this is true, and other DVD media plays just fine, then you probably want to pick up a different brand of disc and try again.
I hope this helps!