Where are my toolboxes and models being created and stored?

Answer

By default, all user-created toolboxes are created in the User Profile folder. The User Profile is located in the following location:

Windows XP:

C:\Documents and Settings\<user profile>\Application Data\ESRI\ArcToolbox\My Toolboxes.

Windows 7, 8, 10:

ArcMap

C:\Users\<user_name>\AppData\Roaming\ESRI\Desktop<version>\ArcToolbox\My Toolboxes

AcGIS Pro

C:\Users\<user_name>\AppData\Roaming\ESRI\ArcGISPro\ArcToolbox

Any models created within a user-created toolbox are stored in this location as well, as a part of the toolbox.