Do you have a SoundBlaster Audigy card as piaproxy.dll is part of the Audigy
device drivers.  Try reinstalling the drivers.  If that doesn't help check
with Creative support giving full details of the error (which you omitted when
posting your message here) and see if they are able to help you.

When do you see the error involving mfc42.dll and in what circumstances?  If
immediately following the piaproxy error forget about it until you sort out
the piaproxy.dll problem.  If not related to the piaproxy.dll error then
please post full details of the error message you are seeing and the
circumstances in which you see it - such as when opening Windows Explorer.