Time Machine via Airport Express

Hello Folks.
I have a new Macbook Pro with the Time Machine feature and wonder if it can be used Wi Fi with an external hard drive plugged into the Airport Express? I have an external hard drive (not Mac) and am hoping that will work without going to the Mac Time Capsule.

What do you think?

And also, I'm still using an older IMac with Tiger OS......if I upgrade it to Snow Leopard will that machine also backup to the same hard drive? (I'm assuming Time Machine will create a new directory for the second machine?)

NOTE: Thread moved to appropriate forum. Not just anything goes in Anything Goes

That should work fine. Both machines should be able to backup to the drive though you will usually need to format the drive to HFS+. I have seen some reports of other formats being used over networks but haven't tried it. The backups will be stored in separate sparse bundle files.

If possible do the initial backup by an Ethernet connection. The initial backup can take quite some time.