Hi See bug: http://hackage.haskell.org/trac/ghc/ticket/1590 Currently the recognised way to test if your application is being run on Windows is: import System.Info .... = os == "mingw" This is wrong on so many levels! # The return result of os is NOT an operating system # The result mingw does not imply that mingw is installed # String comparisons are not very safe, a typo stops this working # In GHC this comparison will take place at runtime, even though its a constant Since nearly all uses of System.Info.os are to check if the operating system is Windows, adding an explicit isWindows function would simplify things. Proposal: Add System.Info.isWindows :: Bool This value should return True on all Windows systems (Win 1.0 ... Vista), and False on all other systems. Thanks Neil