The first VEB will NOT format the destination harddisk. It is when you create the recovery media to a USB disk or something that it will be formatted to make it bootable, but you don't put (in most cases) that recovery image on the same large drive as your backup disk. A simple 2 GB USB thumbdrive does the trick
Being able to backup several computers to one harddisk is not an issue. I do this all the time. I backup every computer under a folder BACKUP and the solution creates subfolders with the name of the computer
Best wishes also!