I have some burnt CDs that when I try to open them I get the message "The disk in drive D is not formatted. Do you wish to format it now? Yes/No". If I click no then I can't read the CD and if I click Yes it says that the disk cannot be formatted. Why is this happening and how can I fix this?

Sounds like you have InCD installed. It is packet writing software usually bundled with Nero. I don't know if DirectCD works the same way. If this is the case turn it off and you'll be OK.

It could be the CD-R's as well, some drives cannot read some discs burned on other drives. This compatiblity prob was dealt with until the 80 min, 700 mb cdr came out. Now compatiblity probs are back. Also CD-r's are sensitive to light, too much exposure can "lighten" the dye on the disc, making it harder to read and some drives think there's no format or data to read.