Index: uspace/app/sysinst/sysinst.c
===================================================================
--- uspace/app/sysinst/sysinst.c	(revision 6d06bbc3a0829fbe3acfa52ab71f7c17bd217eaa)
+++ uspace/app/sysinst/sysinst.c	(revision a2f95cec4fce319db3929663aa2b41d232fef6b9)
@@ -143,4 +143,12 @@
 };
 
+static void sysinst_upgrade_confirm_button(ui_msg_dialog_t *, void *, unsigned);
+static void sysinst_upgrade_confirm_close(ui_msg_dialog_t *, void *);
+
+static ui_msg_dialog_cb_t sysinst_upgrade_confirm_cb = {
+	.button = sysinst_upgrade_confirm_button,
+	.close = sysinst_upgrade_confirm_close
+};
+
 static errno_t sysinst_restart_dlg_create(sysinst_t *);
 static void sysinst_restart_dlg_button(ui_msg_dialog_t *, void *, unsigned);
@@ -163,4 +171,5 @@
 static errno_t sysinst_eject_dev(sysinst_t *, service_id_t);
 static errno_t sysinst_eject_phys_by_mp(sysinst_t *, const char *);
+static errno_t sysinst_upgrade_confirm_create(sysinst_t *);
 
 static futil_cb_t sysinst_futil_cb = {
@@ -251,4 +260,51 @@
  */
 static void sysinst_confirm_close(ui_msg_dialog_t *dialog, void *arg)
+{
+	sysinst_t *sysinst = (sysinst_t *) arg;
+
+	ui_msg_dialog_destroy(dialog);
+	ui_quit(sysinst->ui);
+}
+
+/** Upgrade confirm dialog OK button press.
+ *
+ * @param dialog Message dialog
+ * @param arg Argument (sysinst_t *)
+ * @param btn Button number
+ * @param earg Entry argument
+ */
+static void sysinst_upgrade_confirm_button(ui_msg_dialog_t *dialog, void *arg,
+    unsigned btn)
+{
+	sysinst_t *sysinst = (sysinst_t *) arg;
+
+	ui_msg_dialog_destroy(dialog);
+
+	switch (btn) {
+	case 0:
+		/* OK */
+		fibril_mutex_lock(&sysinst->responded_lock);
+		sysinst->responded = true;
+		sysinst->quit = false;
+		fibril_mutex_unlock(&sysinst->responded_lock);
+		fibril_condvar_signal(&sysinst->responded_cv);
+		break;
+	default:
+		/* Cancel */
+		fibril_mutex_lock(&sysinst->responded_lock);
+		sysinst->responded = true;
+		sysinst->quit = true;
+		fibril_mutex_unlock(&sysinst->responded_lock);
+		fibril_condvar_signal(&sysinst->responded_cv);
+		break;
+	}
+}
+
+/** Upgrade confirm dialog close request.
+ *
+ * @param dialog Message dialog
+ * @param arg Argument (sysinst_t *)
+ */
+static void sysinst_upgrade_confirm_close(ui_msg_dialog_t *dialog, void *arg)
 {
 	sysinst_t *sysinst = (sysinst_t *) arg;
@@ -622,4 +678,23 @@
 	rc = sysinst_existing_os_part_find(sysinst, fdev, &part);
 	if (rc == EOK) {
+		/* Open dialog to confirm that user wants to upgrade. */
+		rc = sysinst_upgrade_confirm_create(sysinst);
+		if (rc != EOK) {
+			sysinst_error(sysinst, "Cannot create window.");
+			goto error;
+		}
+
+		fibril_mutex_lock(&sysinst->responded_lock);
+		while (!sysinst->responded)
+			fibril_condvar_wait(&sysinst->responded_cv,
+			    &sysinst->responded_lock);
+		fibril_mutex_unlock(&sysinst->responded_lock);
+
+		/* User decided not to upgrade existing installation? */
+		if (sysinst->quit) {
+			(void)vfs_unlink_path(MOUNT_POINT);
+			return EOK;
+		}
+
 		/* Set mount point for installation partition. */
 		rc = fdisk_part_set_mountp(part, MOUNT_POINT);
@@ -1130,4 +1205,6 @@
 	if (rc != EOK)
 		goto error;
+	if (sysinst->quit)
+		return EOK;
 
 	clean_dev = true;
@@ -1200,4 +1277,10 @@
 	sysinst_progress_destroy(sysinst->progress);
 	sysinst->progress = NULL;
+
+	/* User decided not to upgrade system? */
+	if (sysinst->quit) {
+		ui_quit(sysinst->ui);
+		return EOK;
+	}
 
 	rc = sysinst_restart_dlg_create(sysinst);
@@ -1458,4 +1541,30 @@
 }
 
+/** Create upgrade confirmation dialog.
+ *
+ * @param sysinst System installer
+ * @return EOK on success or an error code
+ */
+static errno_t sysinst_upgrade_confirm_create(sysinst_t *sysinst)
+{
+	ui_msg_dialog_params_t params;
+	ui_msg_dialog_t *dialog;
+	errno_t rc;
+
+	ui_msg_dialog_params_init(&params);
+	params.caption = "System upgrade";
+	params.text = "Existing installation found. "
+	    "Do you want to upgrade it?";
+	params.choice = umdc_ok_cancel;
+	params.flags |= umdf_topmost | umdf_center;
+
+	rc = ui_msg_dialog_create(sysinst->ui, &params, &dialog);
+	if (rc != EOK)
+		return rc;
+
+	ui_msg_dialog_set_cb(dialog, &sysinst_upgrade_confirm_cb, sysinst);
+	return EOK;
+}
+
 /** Create restart dialog.
  *
@@ -1503,4 +1612,7 @@
 	if (sysinst == NULL)
 		return ENOMEM;
+
+	fibril_condvar_initialize(&sysinst->responded_cv);
+	fibril_mutex_initialize(&sysinst->responded_lock);
 
 	rc = futil_create(&sysinst_futil_cb, (void *)sysinst, &sysinst->futil);
@@ -1552,5 +1664,9 @@
 	}
 
-	(void)sysinst_confirm_create(sysinst);
+	rc = sysinst_confirm_create(sysinst);
+	if (rc != EOK) {
+		printf("Error creating window.\n");
+		goto error;
+	}
 
 	ui_run(ui);