The appdata folder on windows is just what it sounds like. It’s a folder that stores application data for some programs. Most programs store some of their application data in the registry and some of it in appdata folder. Your appdata folder is an important folder to back up in case of a computer crash or if you choose to upgrade or install Windows.
To get to your appdata folder:
Windows XP: You can find the appdata folder by navigating to it in Explorer under XP. First Show Hidden Files and Folders then go to My Computer > C:\ > Documents and Settings > <User Name*> > Application Data > Roaming
*Replace <User Name> with your actual user name
Windows 7/Vista: It’s as simple as trying %appdata% and pressing enter into your start menu search box.