This problem is fairly common after certain types of malwareinfections. To fix the Desktop tab problem, open the Registry Editor and go to:
Make sure that a key named ClassicShell exists, and that its value is set to 0. Create this key if necessary.
If you enable the Desktop tab is enabled ad immediately disabled, then there may be a group policy stting causing it to be disabled. The group policy setting controlling this tab’ existance is at:
Local Security Policy: UserConfiguration | Administrative Templates | Windows Componments | Windows Explorer. You must set the Turn on Classic Shell setting to Enable.
The same thing goes for the Screen Saver tab. it is controlled at:
Local Security Policy: User Configuration | Administrative Templates | Control Panel | Display.
You have to set the Hide Screen Saver tav to either Not Configured or to Disabled.
There are two locations in the registry where the screen saver tab is controlled:
In both of these locations, he NoDispScrSavPage value to 0.
As always, back up your machine before editing the registry. Editing the registry is dangerous, and making incorrect modifiecations can destroy Windows.