dvd drive on 2009 iMac desk top won't read dvd whats the fix

The first thing to try is a drive-cleaning disk. About US$5-15 at most computer, office supply, and electronics outlets. Slot-loading drives get quite dirty and that dirt/dust can interfere with proper disk reading. The cleaning disk is an inexpensive and easy step that often fixes the problem.

CD/DVD Drive - Troubleshooting See troubleshooting section.

CD/DVD Drive - Troubleshooting (2

I have seen my PB Pismo optical drive read a DVD one time, then not the next, then read it again! Data disks (CDROM) are more reliable. Some DVDs are made cheaply too.