a) single partition 2 TB external firewire HD w/ 10.5.8 (my current StartUp Disk)
b) single partition bootable USB drive with 10.6.7 (full version / not just an "upgrade" version)
c) single partition bootable USB drive with 10.8.2 (full version / not just an "upgrade" version)
Desired Outcome: run 10.8.2 on the single partition firewire HD (item "a" above)
Constraint: the single partition firewire external HD w/ 10.5.8 (current StartUp Disk) is a 2TB drive, and it also has other (non Mac OSX related) data files on the drive that I do not want to lose. To be clear, the constraint is that I do not want to erase this drive during the upgrade process.
System Details: 2008 Intel iMac 24", 4 gig RAM, USB 2.0, broken-ass internal DVD drive, broken-ass internal HD
My Question: how best to achieve the desired outcome? If not possible, please suggest next best alternative.
My Appreciation For Your Help: sincere & immense :-)