Apparently, Itunes keeps several backups of your IOS devices. If my guess is right, Itunes creates a backup every time there are changes in your IOS devices ie new mp3, video, apps. I does not seem to delete the old backup. So this tip allows you to delete old IOS device backups. The following is the steps for you to delete old IOS backups in Windows.
1. Open Itunes.
2. Under Edit, select Preferences.
3. Preferences Window appears. Select Devices Tab. It will list all your backups of your IOS devices.
4. Select old backup files you think you can dispose and click on Delete Backup.
The procedure above easily cleared my laptop 2Gb of space. I would like to give a word of caution on deleting backups. You should carefully delete old backups which you think you have minimal changes in your IOS devices.