Thanks. So, I can use Time Machine to back up different Macs running different versions of Mac OS using the same external hard drive. Right?
i believe this is true. i haven't actually tried #2
in order to back up more then one mac on one external hard disk you need either:
1) A Time Capsule Wireless Router.
or
2) an external hard disk divided up to multiple partitions. one partition for each computer.
i think #2 is true. if its no longer true then it probably still is the safest thing to do. i thought os x put a token
or a file in the root dir of each hard disk and doesn't like more then one backup set on one partition
like "com.apple.time machine.supported" or something
yeah i knew i was sorta right. the time machine faq also recommends putting it in separate partitions
http://pondini.org/TM/4.html