You need a program like Window Blinds or Ashton Shell.Though Window Blinds uses a variety of skin.Ashon shell has better looking skins. http://www.stardock.com/products/windowblinds/ Then the CPU should automatically recognize the new skin. If not just save the zip file to Hard drive.Then open move all contents into a folder if not in a folder to Window Blinds themes.
lol.. i can't be bothered changing the windows skin.. theres always trubble in doin stuff like that..
The program basically does it for you, it's pretty simple. Try www.download.com and search for LiteStep/WindowsBlinds/ObjectDesktop or one of those programs, install it, and then run it and it has a few skins to choose from. If you want new ones, you need to go download them off the internet somewhere. The program should show you a link.