Application 32 or 64 bit?

Under Windows 7 32 bit applications should be installed under 'Program Files (x86)' and 64 bit under 'Program Files'

How to determine if 64 or 32 bit, for a specific dll or exe file:
Use cygwin and file:

bwalth@gonzales4G /cygdrive/c/Program Files/MATLAB/R2010b/bin/win64
$ file MATLAB.exe
MATLAB.exe: PE32+ executable (GUI) x86-64, for MS Windows

alternativley look at processes in Task Manager 32 bit processes are marked *32