SuperDuper cloned drive not available as Startup Disk

[Lava Lamp Freak]

I'm using my MacBook as my main system while I'm waiting for the new iMacs to come out, and due to limited drive space I am running off of a SuperDuper clone of my last MacBook Pro. I can achieve this by booting while holding down the option key at startup, but it does not show up as an available Startup Disk in System Preferences. The annoying thing is that I can't get to the boot menu with my Apple wireless keyboard which means every time I reboot I have to open up the MacBook's screen and hold down the option key. It would be much easier if I could just set this as my boot drive and be done with it. Any ideas why it isn't showing up?