In order to install any themes you can find on this site, you will have to patch your uxtheme.dll. This is necessary because you are not able to install unsigned themes from 3rd parties. Here comes a short explanation:

Use an Installer (for users without Service Pack 1):

Without Service Pack: VistaGlazz Final 1.0 for SP0 (click me).
With Service Pack: VistaGlazzBeta3 for SP1.

Another one for SP1 I haven’t tried, is available for download here.

How to Install the files manually: (for users with Service Pack 1; experienced users only)
Source

Warning: If you do anything wrong you might not be able to start your PC. We will not take any responsibility for any possible damage. I personally did something wrong on my first attempt, because I unzipped the files but forgot that WinRARusually creates a subfolder. If that happens to you simply start windows via f8, select the starting mode “command line” and move the files to the proper folder (system32). The command to do that is “move [filepath] [destination]“!

1. Login as Administrator

2. Navigate to your system32 folder that is inside in your Windows Folder. (Press Windows Key+E to open the explorer, then navigate to your Windows folder, usually C:\Windows\system32

3. Right-click on the file uxtheme.dll and click on properties.

4. Click on security, then advanced. Open the tab “owner” and click on “edit”. Select your user account and click on “ok”.

5. Repeat steps 3 and 4 for themeui.dll and shsvcs.dll

6. Right-click uxtheme.dll and click properties again.

7. Give yourself (or group) Full Control permissions and close dialogs. Select your user account from the first list and click on “edit”. Select your user account on the following tab again and check “full permissions” (at the very top of the second list). A popup will ask you to confirm that step, click ok again.

8. Repeat steps 6 and 7 for themeui.dll and shsvcs.dll.

9. Rename uxtheme.dll to uxtheme.old.

10. Rename themeui.dll to themeui.old.

11. Rename shsvcs.dll to shsvcs.old.

12. Download the patches files here-> x86 | x64

Unzip the files to your system32 folder and double or triple check that they are NOT in a subfolder!

13. Copy patched files into %systemroot%\System32

14. Reboot (required)

15. Copy a theme you downloaded from this site to the folder C:\Windows\Resources\Themes\

16. If the theme does not contain a .theme then you will have to copy the “Aero” folder and insert the .msstyle there.

17. Enjoy.