PSDs are cross-program and cross-platform.
There's no reason you should not be able to open one in either program, on a PC or a Mac.
How would I get it to open in cs5? It has a pse logo in front of it in the folder and it opens in elements when I click on it.
I got it. Nevermind. Instead of directly clicking on it, I just went to cs5 and to the file dropdown to open, and got to it that way.
I have never heard of a PSD that doesn't open in Photoshop, Debra. Sorry.
Maybe this woudl be a better question for the Photoshop or Photoshop Elements forum rather than the Premiere Elements forum?
Not sure about on the Mac, but the program that a file type Opens in, on a Windows computer, is predicated on the setting for that File Type in Control Panel>Folder Options>File Type. There, one can set the program, and establish that as the default.
With both PS and PSE, it will be the program, that was installed last (by default), but can be changed, as is needed.
As you have found out, one can also choose Open In, to determine the program to be used.
As a "for instance," I have PS on my computers, but for JPEG files, have those set to Open in Ulead's PhotoImpact, rather than Photoshop. For my PSD's, however, I have the setting to Photoshop.