Are you (like me) one of those that extensively use pictures and textures, in several formats? Then you are interested in this product…
I used to have installed the nVidia DDS Thumbnail viewer to be able to see thumbnails of my DDS textures in the explorer. Also used to have another application for TGA files, etc. Apart from the fact that I was still missing some formats, like Photoshop PSD, one day, without notice, my TGA and DDS viewers starting to collide. I could only make one of them working.
Struggling with that problem, I found the MysticThumbs viewer: an application that combines viewing of all the usual formats, including PSD. In addition to that, it has versions for both x86 and x64, something not too frequent in this kind of viewers.
I have tried it for a couple of days, and seems to work pretty well. I´d suggest you to give it a try.