Windroy lets Android run on Windows systems.
Kinda like Wine that lets you run Windows applications on Linux.
mpk.exe is a filename that is used by several legitimate applications.
However, in most instances where that file is found it is
not a legitimate file but malware.
The location of that file as well as the size is a start to see which one it is.
Since avast flags it, I strongly suggest to follow these instructions:
http://forum.avast.com/index.php?topic=53253.0