Where are the Properties.Settings.Default stored?

You can get the path programmatically:

using System.Configuration;  // Add a reference to System.Configuration.dll
...
var path = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal).FilePath;

In order to work with newer versions of Windows' policy of only allowing read access by default to the Program Files folder (unless you prompt for elevation with UAC, but that's another topic...), your application will have a settings folder under %userprofile%\appdata\local or %userprofile%\Local Settings\Application Data depending on which version of Windows you're running, for settings that are user specific. If you store settings for all users, then they'll be in the corresponding folder under C:\users or C:\Documents and Settings for all user profiles (ex: C:\users\public\appdata\local).

thanks for pointing me in the right direction. I found user.config located at this monstrosity: c:\users\USER\AppData\Local\COMPANY\APPLICATION.exe_Url_LOOKSLIKESOMEKINDOFHASH\VERSION\user.config.

I had to uprev the version on my application and all the settings seemed to have vanished. application created a new folder with the new version and used the default settings. took forever to find where the file was stored, but then it was a simple copy and paste to get the settings to the new version.