Windows 7 themes corrupted

Question

I have difficulties changing Windows themes. Whichever theme I try to use, it's just appear black. (It appears blank even in Personalize Desktop settings.) Aero does work, but I can't set background or any other theme.

This happened after I switched to windows classic and then back to aero (I was trying to solve images thumbnails, that would not preview Large icons (they were just white)).

I have tried:

Registry changes, such as:

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System]
“Wallpaper”=-
“WallpaperStyle”=-

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System]
“Wallpaper”=-
“WallpaperStyle”=-

Wiping off slideshow.ini file in Themes folder.

Renaming TranscodedWallpaper.jpg to .old.

adding ActiveDesktop to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies

sfc /scannow
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Windows\system32>sfc /scannow

Beginning system scan.  This process will take some time.

Beginning verification phase of system scan.
Verification 100% complete.

Windows Resource Protection did not find any integrity violations.

C:\Windows\system32>

    downloading new theme from windows
    restarting Themes service

Nothing worked. Help?

Answer 1

It it possible that your windows 7 is not activated? I read somewhere that windows will remove the background in such a cases.

Answer 2

I obtained ownership of registry entry:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows

then changed permissions for admin and myself, then removed "deny everyone" - and everything worked again.