Hello, have you checked the BIOS chipset drivers yet ? Run free program of Speccy : Speccy - Download . Get free version, look at the motherboard information and take note of Bios information, you may need to go to the motherboard manufacture or the computer manufacture, get latest Bios chipset for your computer and motherboard type, and if needed , go ahead and install new ones, you may have a driver issue or you may not, I got my chipset from my computer manufacture, which would be my first choice. See if this helps out, failing the chipset drivers being bad, with all the other diagnostics you have done, it would seem as if the drive is having hardware issues.

Samantha,
Take a DVD that cant be read and try in another computer; lets be sure of the cause.
If it still does not work, go to search by start button and type device manager. Update drivers for all drives.
The actual hardware may be defective, too, dont overlook that.

Here you go, also read above posts.
BIOS: frequently asked questions

You must update the BIOS, unless you feel comfortable, you may want to get help. It is not a difficult thing to do, but if done incorrectly you will have problems.
How to Update Your BIOS | PCWorld

It is an easy job, to update bios. A high school kid, could probalby do it and be happy with just a small payment.
I do wish you luck.