Many users choose to “tune” their themes , giving them a different look to your operating system and the truth is that some manage to do it in a very striking way.If you are one of them,I am sharing an excellent site that shares many themes.
Skin Packs is a site where we can find a lot of themes for Windows XP, Vista and 7 completely free .
There are a variety of themes available, you can change the look of your Windows and make it look like Mac, Android, Ubuntu, Windows 8, Xbox 360, etc.. Each of the themes brings all the requirements needed to install, as well as the operating system with which they are compatible.
For users who want their Windows look like Mac, should download a dock that looks better.
Finally, we recommend that before installing any of these, make a backup of your data in case if something goes wrong.
Link: Skin Packs