If all the multiple files are the same size, you can use ImageReady to import the files as layers. To do this, open ImageReady and select File>Import>Folder as Frames. The size of the resulting file will be based on the dimensions of the first file in the folder that is opened. You can then transfer the layered image to Photoshop by click the "Edit in Photoshop" tool at the bottom of the tool box.