System Tools

On April 3, something totally crashed,now my restore will
not let me restore before that point. I also can not use
any of my system tools since that day. Every time I try
to use them I get this message-
mmc.exe-Bad Image
The application or DLL
C:\Windows\system\MFC42u.DLL is not a valid Windows
image. Please check this against your installation
diskette.

Of course I did not get a diskette since I am supposed to
be able to restore,but it won't let me get to that point.
I don't know what happened,it just started going nuts,and
now I don't know how to fix it. Any help would be greatly
appreciated!!