A problem relevant to windows XP

I used Microsoft Windows XP as operating system. Recently I am getting a problem. When I am trying to run programs, games. I keep getting these following error message.
Error code: The application or DLL C:WINDOWSsystem32oledlg.dll is not a valid Windows image. Please check this against your installation diskette.
I am not an expert with computers. Please tell me what to do to fix this problem.
