I need to do a temporary 'mirror' of my wife's Win 7 laptop until I get a more permanent system put together. Her HDD is 640 Gigs, but only about 60 are being used by all software in total. I was going to do a mirror backup to my WD portable that currently has about 80 gig open, but I can free up more if needed. Again, this is intended to be temporary until I install the new 500 Gig HDD in my PC. My 'mid-term' plan was that I would back up my 500 HDD to hers and hers (640 HDD) to mine, etc, since we each only use about 60 Gigs total on our existing drives. That way I would utilize the open space that's not going to be used on either drive for a long time... or at least until I set up a separate external HDD for everything. My question is that I just read that supposedly the 'target' drive HAS to be larger than the 'source' drive. That would mean I need an extra drive of at least the 640 Gig that she's got. Is this right or not??? If so, how the heck am I going to match drive sizes when the typical HDD for my desktop is either 500, 750, 1T, 1.5T, or 2T, etc... ??? What am I missing here? Thanks!