Da Da ! My new BIAB finally got here.

I got the 80 GB External Hard Drive version... and the printed instructions tell me I can run it directly on the hard disk or install it on my system.

My question... can I do both... install it on a laptop for a gig... and still have it on the external Hard Disk to run on my desk top at home for rehearsel or arranging or whatever?

OR... once you "install" it on your system is it no longer useable on the external hard disk?

Thanks for any help.