Use INVALID_FILE_ATTRIBUTES to test for failure of
GetFileAttributesA/W and not -1 or 0xFFFFFFFF.

diff --git a/programs/winhelp/macro.c b/programs/winhelp/macro.c
index 8b39fb2..c25d209 100644
--- a/programs/winhelp/macro.c
+++ b/programs/winhelp/macro.c
@@ -506,7 +506,7 @@
 BOOL MACRO_FileExist(LPCSTR str)
 {
     WINE_TRACE("(\"%s\")\n", str);
-    return GetFileAttributes(str) != 0xFFFFFFFF;
+    return GetFileAttributes(str) != INVALID_FILE_ATTRIBUTES;
 }
 
 void MACRO_FileOpen(void)