Try to open Registry Editor by typing
regedit in RUN dialog box. If u get an error that "Registry Editor has been disabled by the administrator", then ur system has been infected by a virus
Scan ur computer with a good anti-virus!
And if u r able to open regedit then just goto:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
and in right-side pane delete the key
NoFolderOptions