Quantity of downloads

I’m about to purchase Cubase 7 Elements (download) but I don’t have my own computer yet. Will I be able to use my sister’s computer now and download it again later when I get my own computer?

Yes, but you will have to go through a reactivation process.
Described here…
http://www.steinberg.net/forums/viewtopic.php?f=25&t=25117

Thank you.