I don't like the fact that a lot of programs will leave files on a computer when they are uninstalled, so I have tried to minimise this with Digital Fake Book. All automatically written files are saved to one location and I avoid using the registry.
If you have installed Digital Fake Book from the normal installer, it can be uninstalled from the Add or Remove Programs control panel the same as most other programs.
The data folder will not be removed automatically by the uninstaller if you have run Digital Fake Book as it will contain a backup file of the song data called DfbSongData.bak. If you want to remove all remaining traces of Digital Fake Book, this folder will need to be manually deleted.
On Windows XP the data folder can be found here:
(eg. C:\Documents and Settings\Mike\Application Data\DigitalFakeBook)
On Windows Vista and 7 the data folder can be found here:
(In both these examples "Mike" will be your user name.)
Other than that, the only files left will be ones you have saved yourself from the export functions.
In the portable version all files are contained in the main folder or subfolders under the main one, so to remove it you simply need to delete the folder. Note: any songs you have created will also be deleted.