求高手指点: IE>tool>Internet options it locked

自从中了71791.com 的毒以后, IE window's pulldown menu, tool>internet options is locked. A window error window pop up, says: "This operation has been cancelled due to restrictions in effect on this computer. Please contact your system administrator."
this is an old computer with win98 SE. I guess it can be removed in hkey. But don't know which one.
Please help and Thanks in advance.