Installing System 10.5 on External Hard Drives

[hwmillerster]

I have a problem: I have two external hard drives, a USB 500 GB Maxxor and a Other World Computing miniStack v3 1 TB using the optional Firewire 800 connection. I cannot get the system to mount on either hard drive and both are extended journeled. The Maxxor is partition into 2 equal 250 GB sectors. The miniStack is not. When I attempted to install 10.5 onto it, the Maxxor partitions had big exclamation marks and the miniStack didn't show up at all? Everyone I talk to says that any journaled hard drive should be able to have the system mounted. I didn't have this problem when I had my previous Mac, a 2000 iMac DV and a OTC 80 GB hard drive. Solutions?