have this same problem but first with Internet Explorer attempting to "open" all the .exe programs ... and then after tring to "fix" the problem ... now Word attempts to open the .exe when launched ...
I ran down some answers through Google but lost them ...
the problem seems to be that you have "associated" the .exe file extension with a specific program (in your case media center) ... this is that lovely helper that pops up when you try to open an "unknown" extension program and the default is to use your selected program to open all files of this extension ...
I think this happens by mistake or somehow automatically when downloading some exe file or something (I believe it was a java updatate here)
if I find my solution I will post ... for now go to the Run option off of the start button and "run" your program ... you will need it's name or browse to it
that seems to work for me ..
thanks