Thisworkbook.path Works if on USB drive, but not if on Desktop

You'll probably find it one directory up the tree. Instead of being in 'c:\users\name\desktop' it'll be in 'c:\users\name' and the file name will start with 'desktop...'

The Path property (of any object - workbook, application) returns a path, but it's not terminated with a trailing '\'. If the file is located in the root directory of a drive (any drive - not particular to your USB drive), it returns 'Z:' which then gets (assuming that cell C3 contains 'test') 'test SlideMain.csv' appended and 'Z:test SlideMain.csv' is a valid file path.

If you try to save it in the Desktop directory, the constructed file name will be 'C:\Users\Name\Desktoptest SlideMain.csv', which is not exactly where you want it to go, but a valid path, nonetheless...

Simple debugging, testing the constructed file name, would have saved you some time...