I have a Windows 7 PC, and since a couple of days ago if I try to open notepad i get the following error:
Windows cannot find
C:\Windows\System32\notepad.exe. Make sure you typed the name correctly, and they try again.
By performing a search I found that notepad.exe in c:\windows, c:\windows\system and c:\windows\system32, and in all three locations I have tried to replace it with the file taken from another Windows 7 PC but I get the same error.