Write violation – MFC42.DLL & MSVCRT.DLL

i always get Access Violation with this 2 files everytime i installed my VB6-compiled EXE into my client’s computer. Doesn’t matter whether the computer is a Win98 or WinNT, they will get this error, therefore all i can do is choose “Ignore” for it. What is causing this? What are the consequences after i chose Ignore to install these files?