Your contractor has either --

1. Replaced the FileOpen menu options and toolbars with their own. You can
fix that by resetting the toolbars (right-click any toolbar, select
Customise, right-click the menu or toolbar, select Reset), or by re-adding
the normal FileOpen function.

2. Written a function called FileOpen, which is running in place of the
built-in function. You can defeat that by finding their function (it will be
in your normal.dot or in an add-in) and renaming it. However, if this is a
corporate-wide thing, you mightn't have the necessary permissions.

Other work-arounds --

1. Go to Tools > Macro > Macros. Select Word Commands from the 'Macros In'
drop down. Select FileOpen from the command list.

2. Create a macro, called anything, containing this line of code --

dialogs(wdDialogFileOpen).Show

Assign that macro to your File menu.