If you want to make the portable hd accessible by both machines at the same time just share the volume in my computer. Right click on the drive, go to sharing and security, check "share this folder on the network", hit ok. Go to second machine, go to sart>run, type in \\(fisrt computer's name)\ and hit enter. Your share should appear, you can just drag and drop to your hearts content
<A HREF="http://www.folken.net/myrig.htm" target="_new">My precious...</A>