Connect one drive between 2 computers?

Hi, People,
What I’ve been trying to figure out for a long time (without trying it out and blowing something up) is whether you can connect an external hard drive through its Firewire connector to one CPU and through its USB connector to another computer and use it for both of them at the same time: for instance, my Shuttle PC and my MiniMac.
Any one have anything to say on this craziness?

Thank you,
Jim Dodds
//email address edited out by imkidd57//

For what I know this is not possible, and actually I think that it is not safe to connect the same disc to two different machines in this way.

If you need to connect the same disk to more machines at the same time, the best option (for what I know) is a NAS, i.e. an external disk provided with a network connection. Connecting the NAS to a hub, you can share it among many machines.

A cheaper alternative is to get a device like this one.