Thanks for your replies.
Windows XP, IE ver 8.0 and it is LCBK.
When I go into my favorites, all the names now have 'locked' in front of them, and they will not open.
If I right click on any favorite and look in properties, general, it says the file type is LCBK where it normally says Internet shortcut.
It must be some sort of virus but I am running AVG anti virus and Windows Firewall, so am a bit confused!!