When you replaced the cd drive, did the new drive require a driver install for that drive? If yes, you might check the website of the maker for any updates to that driver. There's a possibility that the driver has settings/prefs that can be changed.
There's also the posibility that, when you installed the new drive, the settings/prefs for the program being used to burn the cds, got messed up. You might check those and see what options are available.
The only time we run into pc/mac cd problems is when the pc user used a particlular program that makes something like a slide show that only works on pc, but the disc always mounts.
One thng you might try on the mac is to go to system prefs/cds & dvds and play with the settings in "When you insert a picture cd"
Using OSX 10.3.9 on a G4