It's a windows system file (
Microsoft
foundation
classes ) and yes, you do need it or you could have problems opening up all sorts of progs like explorer and outlook.
It can get overwritten by an incorrect version of itself, so the chances are it won't have been the kids.
You need to get a proper version of it, save it onto the root directory of the c drive (ie so that it's adress is c:\MFC42.dll) and then restart windows in safe mode (in normal mode the file should be in use so if you try and correct it, you'll get an access violation message)
Then you'll need to rename the version you have (call it mfc42old.dll) and then copy the new, correct version into your windows system directory.
It needs to go exactly where the current (dodgy) version is....so first do a search for it and write down the address so you know where to put the new version, but it's almost certainly here; c:\windows\system\MFC42.dll
With me so far???
The file is on your windows install disc or you can download a copy of it from here;
http://www.dll-files.com/dllindex/dll-files.shtml?mfc42
If you have a problem doing this in 'safe mode', you'll need to do it in DOS;
* Restart the computer in MS-DOS mode
click the Start button, click Shut Down, In the Shut Down Windows dialog box, click Restart the computer in MS-DOS mode, and then click OK.
* At the command prompt, type: CD\System Press the <ENTER> key
* At the C:\Windows\System prompt, type: Ren mfc42.dll mfc42.old. Press <ENTER>
* Assuming you have a good copy of MFC42.DLL on the root of the C drive do the following...
At the command prompt, type:
Copy c:\mfc42.dll c:\windows\system\mfc42.dll
Press ENTER. The Mfc42.dll file will be copied to the hard drive
* Turn off the computer and after a few seconds back on. The MFD42.DLL file should now be updated.
HTH Charles...good luck
Bill
