METHOD 1:

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

In the right hand area, double click hidden and change the value to 1. Check it in u r tools menu if changes have taken effect.

METHOD 2:

1. Click  "Start" -> "Run"

2. Type "regedit" & then click "ok"

3. Find the key :HKEY_CURRENT_USER\Software\Microsoft\Windows\Currentversion\Explorer\Advanced\Folder\Hidden \SHOWALL

4. Look at the "checkedvalue" key this should be a dword key. If isnt then delete the key .

5. Create a new key called "checkedvalue" as a dword with a value of 1.

6. The "Show Hidden Files and Folders" should now work normally !