I have a cracked version of Minecraft 1.7.4.
I download the skin and change steve.png manually in "versions/1.7.4.jar/assets/minecraft/tex… With new skin that I renamed to steve.png. When I open steve.png now (in entity folder), it is the image of new skin. Then I exit WinRAR and start Minecraft. When I get into the world, it's default skin, not the new skin. When I exit Minecraft and again open the "entity" folder and steve.png it is the default image.
So basically when I start Minecraft it automatically changes skin (or restores/returns back normal) back to default.
This was also happening in 1.7.2 version. In 1.6.2 it worked fine.
I don't care about multiplayer, and never play it. This happens in singleplayer, and I want to make it work in singleplayer.
Also tried reinstalling Minecraft several times. Doesn't work. Tried also in different worlds, new worlds, creative mod etc. Same default skin.
One interesting thing I have noticed is that when I don't delete first steve.png, and then copy new steve.png into the folder, but just copy the new steve.png, it doesn't ask me do I want to overwrite it (old steve.png) it just copies the new steve.png into the "entity" folder.