Hi, Looking at getting an Airport Express. I'm also planning to attach my USB powered external hard drive for wireless backups. This HDD is already getting used for Time Machine backups (when I decide to plug it in and do it manually). My question is, when I plug this in to the express and do it wirelessly, my understanding is that it will re-backup my whole computer (for some reason)... So, will this new backup overwrite all my previous backups?