Mac, please forgive me if this falls under "Teach your Grandmother etc."
but when you ,
....and just stuffed in a Western Digital 320GB drive.
Cloning the original drive was simple with Carbon Copy Cloner.
did you partition the drive GUID?
The reason I ask is that CCC can replicate your previous drive on the new one and everything will seem identical however I found out the hard way that without partitioning the new drive GUID you cannot install any OS updates nor can the OS be re-installed.
The partition need only be a single one, it is not necessary to split up the drive but the Mac system needs the GUID type of partition.
PS. The tech who did this to my MBP was an Apple authorized tech but was not aware of the requirement.
Again if this is not news I apologize but it may be news to others.