Are you sure you want to view all images in Photoshop? The load time for starting up photoshop is a bit of a drag just to view and image. You also can't scroll through a series of images in a folder with it. There are some great image viewers on tucows.com. Ifran is free and I'm not sure about ACDsee, I think the current version is shareware. There are others. I use Photoshop everyday. I couldn't imagine using it as a default image browser. Y
This is stricly my opinion, but I'm convinced that the Ifran and ACDsee give a crisper image that Photoshop too. You can set the image viewrs to open any number of file types.
Just do a search at tucows under "image viewers".