Firewire Drive is my Startup Drive . . . somehow or other
 

I have a small dilemma. I have a Western Digital MyBook that I've backed up my iMac (OS X 10.4.10) to a couple of times now using SuperDuper! I thought everything went well both times.
Upon attempting to back-up today, I discovered that my iMac won't run without the MyBook attached to the iMac and running. When attempting to back-up the "to" drop down list in SuperDuper grays out the MyBook drive (which the SuperDuper! instructions tell me means that the external drive is now my start-up drive). I have no idea how/why this happend.
I'm not sure what to do from here. I have different data on the iMac harddrive v. the MyBook, so if I copy over the MyBook to the iMac this might cause me some problems. My current line of thinking is that I need to copy the system files over to the iMac and hope that the iMac will then become the start-up drive (as it should be). But in the end, I'm pretty clueless about how to extricate myself from this situation and hoped someone would have some prescriptive advice for me.

You should use the "Startup Disk" preference pane to set the proper startup drive, and make certain that you haven't set an "On successful completion" option to set a different startup drive...

Thanks
 

Dave: you were right on the money with your suggestion. Not sure how it happened in the first place, but all seems a-ok now. Thanks!