Open registry editor (regedit).
Start -->RUN -->regedit
Search for showall
you should reach this entry (look at the bottom left corner)
Double Click CheckedValue and enter 1 in the text box.
Incase CheckedValue is not there then right click in the empty space and create a new DWORD value and name it as CheckedValue and initialize it as 1 as described above.
close registry editor and there you go hidden files are visible.