Update INSTALL

Add missing win32-build info and fix one missing statement for unix-build.

INSTALL

@@ -35,5 +35,10 @@ http://www.cmake.org/.
 
 For Unix:
 
-1. cmake -G 'Unix Makefiles'
+1. cmake CMakeLists.txt -G 'Unix Makefiles'
 2. make
+
+For Windows:
+1. Open a command prompt
+2. cmake CMakeLists.txt
+2. Open your default IDE and build it