|There is a great number of reasons for this. Is this your computer or a work computer? If yours then...|
Your computer is logged in as Guest. Log off back to the logon screen and press ctrl+alt+del twice to get the admin logon screen and type Administrator in the logon user name. The password is probably blank unless you set one up when you first installed windows.
Once you are logged on as administrator then right-click the My Computer (on your start menu) then select Manage on the menu. Then select Local Users and Gusts -> Users -> then righ-click on your name. Goto properties -> then the Member of Tab. Make sure you are an administrator and not a guest.
If you can not logon as administrator then I suggest you get professional help.
If you are already administrator then your local GPO has gotten messed up. If this is the case then click Start -> Run -> gpedit.msc. If you are administrator then you should be able to get in otherwise you will get an access denied error. Once in the GP Editor goto
User configration -> Administrative templates ->Windows components -> Windows Explorer
and disabled "Remove the folder options menu from tools options"
Viruses like to turn this off to hide them selves. When was the last time you did a scan on your computer?
If that does not work then try the registry. Start -> Run -> Regedit. Once in the registry editor goto HKLM\Software\Microsoft\Windows\Policy and set the "disable cmd" or "disable Folder Options" to 0 to turn them off.
This requires a high level of computer knowledge. If you are not comfortable with this then I recommend getting professional help.