Eh open photoshop, when you've selected the layer you want to enlarge, click on IMAGE at the top, select Image Size
first tick all the 3 boxes, underneath the boxes you click on "Nearest... ...edges)"
Then make the WIDTH 512 and the HEIGHT 256. then u should have a HD skin. i prefer to color my texturemap in at 256x128, then add some "noise effect" to it. quite easy to color and make skins.
I don't have photoshop, so never mind that :tongue.gif: .