A few days back, a client came to me and told me that he was having 
trouble with his Windows XP. The show hidden files and folders 
was not working at all. If he selected the radio button 
“Show hidden files and folders”, and then press Ok .. the 
changes would just disappear upon opening the dialog again. 
It was probably some virus attack after which the Windows 
registry was not being updated properly. So here is what 
I did to restore it back. There are so many methods to 
restore back the registry. If one method is not working, 
please try another one.

Метод 1 важи, когато проблемът е за текущия юзер.
При метод 2 се редактират настройките за Folder Options.Той се
използва, когато проблемът е за всички юзери и когато метод 1 не
дава резултат.

Method 1:

Go to registry editor by running regedit in the run box.
1. Go to this key:
   HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced

2. Look at the key "Hidden" and change the value to 1.

Now you’re all set to go. Check it in your tools menu if the changes 
have taken effect.

Method 2: (By Random Hajile)

1. Click “Start” -> “Run…” (or press Windows key + R)
2. Type “regedit” and click “Ok”.
3. Find the key: 
   HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
4. Look at the “CheckedValue” key… This should be a DWORD key. 
   If it isn’t, delete the key.
5. Create a new key called “CheckedValue” as a DWORD (hexadecimal) 
   with a value of 1.
6. The “Show hidden files & folders” check box should now work normally. Enjoy! 

Method 3:
If none of the above methods work, please download our 
  Smart Virus Remover from here:

  Smart Virus Remover (625.9 KiB, 230,282 hits)
  http://www.technize.com/?dl_id=6 


Using this Virus Remover please restore your Windows settings 
and your show hidden files and folders will be set to default.

Please spare a few moments from your precious time and tell 
us about your experiences.

========================================================================
По този начин се забранява на юзерите да променят настройките  
свързани с виждането на скритите файлове в системата.

How to disable "Show hidden files and folders" in Folder Option

As you know, you can hide files or folders in Microsoft Windows 
( to hide a file or folder , right click on file or 
folder >select properties and then select Hide file) 
But if you open Folder Option and check "Show hidden files and 
folders " you can see hidden files. 
to disable "Show hidden files and folders" feature follow below steps :
1- Click start > Run > type regedit to run Windows Registry Editor.
2- Go to following address: 

HKLM/SOFTWARE/Microsoft/Windows/Current Version/Explorer/Advanced/Folder/Hidden/SHOWALL

3- In the right panel double click on "CheckedValue" and change value 
   from 1 to 0. Click ok and then exit Windows Registry Editor and restart 
   your computer.
4- Now open Folder Option ( My Computer > View menu > Folder Options)
5- Go to the View tab, in "Hidden files and folders" section, check 
"Show hidden files and folders" and then close Folder Option. 
In future you won't see " Show hidden files and folders" in Folder Option.