Q: Discs on my mac are not being acknowledged

Any kind of disc?  Audio CD, DVD, data (e.g., software installer)?  Even with iTunes not running?

I'd say it is 90% likely you need a new optical drive.  They only last 4-5 years.

http://support.apple.com/kb/TS2288 - Troubleshooting a CD-ROM or DVD-ROM Disc That Does Not Appear on the Desktop

http://discussions.apple.com/thread.jspa?threadID=1953208 - optical drive problems troubleshooting

You can try a drive cleaning disc for about $10 but I have yet to see one cure a drive where I have had problems.