Each item in a VSS project must have a unique name. This error has the following causes and solution:
You have attempted to name a file or an immediate child project with the same name as the project. (An item with that name can exist in other projects in the database, including subprojects.)
You are using both a 16-bit version and a 32-bit version of VSS for the same project and file names are not being mapped accurately.
To resolve this error, give the new item a different, unique file name. Or, you can delete or rename the existing item.
Note File and project names in VSS are not case-sensitive. For example, if you have a file named Test.C, you cannot create a subproject or file named "Test.c" or "test.c" in the same project.