Using a console application, I did this:
vb.net Code:
  1. Module Module1
  2.     Sub Main()
  3.         Select Case IntPtr.Size
  4.             Case "4"
  5.                 Console.WriteLine("32-bit Platform Detected!")
  6.             Case "8"
  7.                 Console.WriteLine("64-bit Platform Detected!")
  8.             Case Else
  9.                 Console.WriteLine("No clue what architecture this is!")
  10.         End Select
  11.         System.Threading.Thread.Sleep(3000)
  12.     End Sub
  13. End Module
I have a 64-bit OS and it wrote that it found a 64-bit. My friend has a 32-bit OS and it said it was a 32-Bit. I think we can say IntPtr is reliable as of this state (well at least on my two tests.)