As Mac users, we often take for granted that the OS works with all Mac hardware.
Sometimes what can appear to be a hardware issue (the sound card not showing up in System Profiler) is in fact caused by an incompatible version of the OS.
The 13″ MacBook Pro sound card requires a slightly different OS driver that only comes with the OEM install disks (10.5) for this book. If you attempt to install another version of 10.5, the sound card will not show up and there will be no audio out through the speakers or headphone jack.
We saw this kind of issue previously when the PPC models starting including the scrolling trackpad. Only the OEM install disks could be used to install the OS in order to get the trackpad to work.
What can make this even more tricky is that if the wrong version of 10.5 is installed on a 13″ MBP, only a clean install with the right OEM disks will install the right sound drivers (Archive and Install & Software Update won’t work.)
If you need to re-install your OS, use the disks that came with your Mac first and then run Software Update. Installing 10.6 will also fix this issue.