Direto da Microsoft :
Learn How to Spot a 16-Bit Application
Because most Windows 3.x–based
programs run properly under Windows
XP, it's sometimes difficult to tell
16-bit and 32-bit applications apart.
Here are two methods for determining
whether an application is 16-bit or
32-bit: •
Right-click the program's executable
file and then choose Properties. If
you see a Version tab, it's a 32-bit
program. •
Or, if the program is running, press
Ctrl+Shift+Esc to open the Windows
Task Manager. On the Processes tab,
look in the Image Name column for the
name of the program's executable file.
If any 16-bit programs are running,
you'll find an entry for Ntvdm.exe,
the virtual DOS machine. Just above it
in the list, you'll see indented
entries for Wowexec.exe (the Windows
on Windows subsystem) and the
executable name of each 16-bit program
running in that virtual machine.