You haven't downloaded a texture skin renamed it to .zip extension and opened it.
In it you'd find a .texture file and a .tga.
There is no .uis file.
The .texture file is made through WB7 as described in the tutorial link I posted above:
[Frames.Texture]
Image=Textures\WHATEVER YOUR TEXTURE IS CALLED.TGA
Tile=1
Trans=1
PerPixel=1
AlignLayerMode=1
AlphaMode=120
[Taskbar.Texture]
Image=Textures\CLOTH_BLUE.TGA
Tile=1
Trans=1
PerPixel=1
AlignLayerMode=1
AlphaMode=120
[StartMenu.Texture]
Image=Textures\CLOTH_BLUE.TGA
Tile=1
Trans=1
PerPixel=1
AlignLayerMode=1
AlphaMode=120