diff --git a/hello.asm b/hello.asm
index 8ec7c45..0974a6b 100644
--- a/hello.asm
+++ b/hello.asm
@@ -51,9 +51,14 @@ process_event:
 	push es
 
 	; On entry, ds and es will not be set correctly for us
-	mov bp, cs
-	mov ds, bp
-	mov es, bp
+	; WM_OPEN_FILE needs ds to be left-as is
+	cmp al, WM_OPEN_FILE
+	je .no_set_ds
+	push cs
+	pop ds
+	.no_set_ds:
+	push cs
+	pop es
 
 	cmp al, WM_PAINT
 	jne .not_paint
@@ -79,6 +84,12 @@ process_event:
 	jmp .end
 	.not_unhook:
 
+	cmp al, WM_OPEN_FILE
+	jne .not_open_file
+	call event_open_file
+	jmp .end
+	.not_opend_file:
+
 	.end:
 	pop es
 	pop ds
@@ -316,7 +327,7 @@ event_click:
 ; out:
 ;  clobbers everything
 event_keyboard:
-	; Unlike other events, keyboard events are not forwarded
+	; Unlike most other events, keyboard events are not forwarded
 	; Since we do not care about the keyboard for this app, we just
 	; swallow the event
 	ret
@@ -353,6 +364,24 @@ event_unhook:
 		mov ax, [window_next]
 		ret
 
+; in:
+;  al = WM_OPEN_FILE
+;  ds:cx = filename
+;  ds ≠ cs
+; out:
+;  ds = cs
+;  clobbers everything
+event_open_file:
+	; File open events are sent specifically to a process, so we don't
+	; need to forward it
+	; Unlike other event handlers, event_open_file is called with ds
+	; still set to calling process's segment, so that it can read the
+	; passed-in filename. For simplicity of code running after the,
+	; event handlers, we set ds to point to our own segment on return
+	push cs
+	pop ds
+	ret
+
 ; ------------------------------------------------------------------
 ; Event handler subroutines
 ; ------------------------------------------------------------------
diff --git a/memory.asm b/memory.asm
index e4ce624..0ca04ff 100644
--- a/memory.asm
+++ b/memory.asm
@@ -72,6 +72,12 @@ process_event:
 	jmp .end
 	.not_unhook:
 
+	cmp al, WM_OPEN_FILE
+	jne .not_open_file
+	call event_open_file
+	jmp .end
+	.not_opend_file:
+
 	.end:
 	pop es
 	pop ds
@@ -297,7 +303,7 @@ event_click:
 ; out:
 ;  clobbers everything
 event_keyboard:
-	; Unlike other events, keyboard events are not forwarded
+	; Unlike most other events, keyboard events are not forwarded
 	; Since we do not care about the keyboard for this app, we just
 	; swallow the event
 	ret
@@ -334,6 +340,24 @@ event_unhook:
 		mov ax, [window_next]
 		ret
 
+; in:
+;  al = WM_OPEN_FILE
+;  ds:cx = filename
+;  ds ≠ cs
+; out:
+;  ds = cs
+;  clobbers everything
+event_open_file:
+	; File open events are sent specifically to a process, so we don't
+	; need to forward it
+	; Unlike other event handlers, event_open_file is called with ds
+	; still set to calling process's segment, so that it can read the
+	; passed-in filename. For simplicity of code running after the,
+	; event handlers, we set ds to point to our own segment on return
+	push cs
+	pop ds
+	ret
+
 ; ------------------------------------------------------------------
 ; Event handler subroutines
 ; ------------------------------------------------------------------
diff --git a/shell.asm b/shell.asm
index cdf639f..dcacbb5 100644
--- a/shell.asm
+++ b/shell.asm
@@ -150,8 +150,11 @@ process_event:
 	cmp al, WM_UNHOOK
 	jne .not_remove
 	call unhook
+	jmp .end
 	.not_remove:
 
+	; We ignore WM_OPEN_FILE
+
 	.end:
 	cmp byte [open_windows], 0
 	jne .windows_open
diff --git a/viewer.asm b/viewer.asm
index 1bdc08f..acfa540 100644
--- a/viewer.asm
+++ b/viewer.asm
@@ -87,9 +87,6 @@ process_event:
 	cmp al, WM_OPEN_FILE
 	jne .not_open_file
 	call event_open_file
-	; Set ds in case event_open_file didn't
-	push cs
-	pop ds
 	jmp .end
 	.not_open_file:
 
@@ -757,7 +754,9 @@ event_unhook:
 ; in:
 ;  al = WM_OPEN_FILE
 ;  ds:cx = filename
+;  ds ≠ cs
 ; out:
+;  ds = cs
 ;  clobbers everything
 event_open_file:
 	; Copy the file name over