how to associate .m file with meditor.exe in Matlab R2010b

Hello profs,

      I just installed Matlab R2010b in my Win7 platform, but I found .m files not opened automatically. So I try add the matlab.exe into the opening application. 
      When I opened .m files every time, matlab.exe was started at the same time. I remembered the times when I used matlab6.5 and .m files were opened by meditor automatically not with matlab.exe started. I hate the matlab.exe started when I just open .m to edit or have a glance.
      Anyone can tell me how to fix the problems in Matlab R2010b? I tried many ways to fix it but failed.