Cannot eject western digital passport

I've had similar problems with external drives. First of all if you have OS 10.4 it will recognize and format external drives that OS 10.5 will not. However the most recent update fixed some issues, so download the most current update by going to the apple and 'software update'. Next, if time machine has stamped the drive, then it will always 'see' the WD drive as the default backup and will write data to it periodically in automatic backup mode. If there is no data on the drive, or if you don't want to save the data then you could reformat the drive (first turn OFF time machine) by going to utilities and then 'disk utility'. If not, then try going to utilities and then use the 'air port' utility to work with the drive as it should be listed on the left as a time capsule.