Have you tried rebooting the computer? If you have norton utilities as well as AV run disk and then win doctor and let it try to fix your registry. Data doesn't change on a CDR once it's burned it can't be rewritten unless its a CDRW. Are all your disks showing CDA extensions or just "open Session" disks? Put in windows, bryce, or some CD where you know the content is not CDA (CD Audio). If it's an autostart CD you can right click on the drive in explorer and press explore instead of open to browse the files. Look and see if the known CD still shows the same CDA files and also if the same names are on each. Try a different CD. Are the names exactly the same? Your Atapi or scsi CD driver is corrupt. The cure is to remove the CD drive from the software system and reboot, then allow Windows to reinstall the drivers. You will also need to reinstall nero. If the names on the CD are different but all have the cda extension it's probably the last audio player or upgrade you installed or nero. Try uninstalling and reinstalling the software. Let me know if any of this works and also a little bit more about your operating system. Any other problems, system crashes, do you shut the power off without shutting down, are there disk errors popping up when you run scandisk?