Checking if file is 32bit or 64bit - on Windows

You can use GNUfile for windows.
You can run the app thru PEID Lastly (and preferred- less room for error) With either Visual Studio C++ (at least express edition minimum) or the Platform SDK installed you can use dumpbin /headers to look at the PE header values.

The first value in the file header tells you the architecture: either 0x14C for x86 or 0x8664 for x64

You could run the 'file' command from linux in a cygwin environment to test.

You could also place some debug statement like 'print sizeof(int)' (schematically) to check.

Just run it and have a look at the Processes tab in Windows Task Manager. If there is a *32 suffix after the process name, it's 32-bit, otherwise it's 64-bit (provided you're on a 64-bit OS).