Tuning files are important for repeat tunings. They store the inharmonicity measurements and your exact adjustment of the tuning curve. Using a tuning file from an earlier tuning saves you from having to measure the inharmonicity and adjust the tuning curve again. Here are some hints on how to organize and backup your tuning files.
TuneLab Pro (for laptops):
TuneLab Pro offers the option of storing tuning files in the TuneLab folder under the My Documents folder. When you store tuning files, you can store them all in that folder, or you can create sub-folders under TuneLab to form categories, such as Churchs, Homes, and Schools, or Grands and Uprights or whatever categories you like. By using sub-folders you can make it easier to browse through a large number of files. You can create sub-folders when you save a tuning file by clicking on the Create New Folder icon show here:

The subject of backing up documents is covered extensively by others, so I will not dwell on it here, except to say that hard disk crashes do happen. Making a CD or diskette of your TuneLab documents folder every so often is good insurance.
TuneLab Pocket (for Pocket PCs):
Tuning files in TuneLab Pocket have always been stored in the My Documents folder, and you can continue to store all your tuning files in that one folder. You cannot create sub-folders at the time you store your tuning files from TuneLab, but you can create sub-folders of My Documents ahead of time, and then select them when the time comes within TuneLab. Use the Pocket PC program File Explorer found under Programs. Navigate to the My Documents folder, and then use the Edit menu of File Explorer to create a new folder under My Documents. Create whatever categories you like, such as Grands and Uprights. Then when the time comes to store a tuning file, you can select one of those folders as follows:

By tapping in the folder field you can choose another folder. Notice that this choice restricts you to one level of sub-folder. You cannot access a sub-folder of a sub-folder of My Documents. This is an inherent limitation of the Pocket PC and has nothing to do with TuneLab.
Then, when it comes time to open a tuning file, you can choose to see all the tuning files at once, or restrict you view a single sub-folder of My Documents as follows:

Unlike the laptop environment, the Pocket PC Open File box can show you all the files in all the sub-folder of My Documents at once. Each file is tagged in the list by which folder it is in.
Backing up your Pocket PC files is a little more involved than backing up laptop files. Here are two options that are explained more fully: