My skins_y folder apparently holds all downloaded high res skins.
however they all appear to be .DDS files which dont seem to do much. can anyone help??

Help you with what?

.dds is used because I think they give better quality (could be wrong) Also keeps the skins that little bit more private as well, as you need a .dds viewer/converter if you wanted to convert them into .jpg files and use them yourself.

You can download a plugin for photoshop and I think there is something that allows you to see them in the windows viewer as well.

.DDS files are used because they do not need to be converted by your graphics card to be used; jpg files do need to be converted. This basically just speeds up loading times, and maybe an extra FPS or two.

Quote from tolkien :

does anyone have a program (or something?) so that i can see them (instead of the randomly placed "windows can't make a preview of this file" screen?

~tolkien

well you could move them from the folder where you found them to your skins DDS folder and preview them in-game.
thats what i usually do.