Have you replaced the optical drive cable? There are many small wires in an optical drive cable, some that control the power, and some that control data. Sometimes the data wires get crimped but the power wires are functional, causing a drive to seem to work and take in a CD, but then not read it correctly or respond to eject commands, etc.
If you can let us know the last 3 of your serial number, we can look up the proper cable.
If the problem is not the cable or the drive itself (assuming you've replaced the drive with a known-good drive, and cable), I would reset the PMU and PRAM, and then also try booting to a different volume in order to rule out software as the culprit.
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Do the disks work normally in other players (music, dvd or computer). Is the replacement Optical Drive is new? Have you replaced the ribon cable?
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Apple MacBook Pro "Core Duo" 2.16 15" Specs
Identifiers: MacBook Pro (Glossy) - MA601LL - MacBookPro1,1 - A1150 - 2101
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