On a PC the backups are stored in “Users\(username)\AppData\Roaming\Apple Computer\MobileSync\Backup”.
Select File–>Get Info and look at the “Size” figure.Find and select (single click) the folder “MobileSync”.Click on the desktop to make sure you’re in the Finder, hold down the Option key, and choose “Go–>Library”.If you want to see how much space is being used by iTunes backups on your computer: Seeing Exactly how Much Space iTunes Backups are Using (totally optional, for the curious) On a Windows computer it’s not so easy to see exactly how your files are using up disk space, but it’s easy to check in iTunes to see if there are any backups you are ready to get rid of.
One thing that is grouped in this category is old iTunes backups. If you’ve ever looked at the Apple–>About this Mac/”Storage” section on your computer, you may have noticed that there is a chunk of storage space being used by “Other” files. If you’re concerned about storage space on your computer, consider removing old iTunes backups.