My C:\Users\Scott\AppData\Roaming\Apple Computer\MobileSync was almost 25 gigs and on a 256 gig hard drive, that’s 10% and that’s tight. I wanted to move it but there’s no officially support way.

Here’s a way. It’s totally not supported and could totally screw up your computer, so you’ve been warned. Remember that you googled your way to this blog and I’m just a random guy. No warranty, Dear Reader. If you are reasonably savvy and you understand that this Works On My Machine, then we’ll get along fine.

Here’s the idea. You’ll move it to a drive with more space, but you’ll LIE to iTunes using a little-used Windows Utility that will make a LINK between the folder iTunes expects to find and the folder you want your backups in.

  • First, make sure iTunes isn’t running
  • Now, move the C:\Users\(yourname)\AppData\Roaming\Apple Computer\MobileSync\Backup\ folder to your preferred location. My was F:\iTunesMobileSync. This is up to you.
  • Finally, start a command prompt as an administrator. You can do this from the Start Menu, type cmd.exe, then right click and select Run As Administrator. From the command prompt, create an junction point as I do below, just change f:\yournewfolder with your new location.
    • One thing to to make sure of, don’t end up with a folder like f:\yournewbackupfolder\Backup\Backup, so be sure to check how your folders ended up when you moved them.
mklink /J "C:\Users\yourname\AppData\Roaming\Apple Computer\MobileSync\Backup" "f:\yournewfolder\Backup"

You should see something like this in Windows 7. Note the little “shortcut” overlay icon? That’s saying this is a link.

MobileSync as a Junction Point

You can also confirm it with dir from the command line. Note the <junction>:

C:\Users\Scott\AppData\Roaming\Apple Computer\MobileSync>dir

 Directory of C:\Users\Scott\AppData\Roaming\Apple Computer\MobileSync

11/25/2011  10:10 PM    <DIR>          .
11/25/2011  10:10 PM    <DIR>          ..
11/25/2011  10:10 PM    <JUNCTION>     Backup [f:\iTunesMobileSync\Backup]
               0 File(s)              0 bytes
               3 Dir(s)  97,594,851,328 bytes free

If you are still on XP and not Vista or Windows 7, you don’t have mklink, but you can use the junction utility in the same way.

Again, if these instructions don’t make sense do you, I urge you to find a techie and please, be careful. You’ve been warned. That said, I’ve just opened up 25 gigs on my C: drive, so I’m happy.

Source: http://www.hanselman.com/blog/HowToChangeTheLocationOfYourIPhoneBackupAndITunesMobileSyncBackupFolder.aspx