show OK instead of Yes/No if reinstalling

The messagebox for the "is already installed, please
reinstall first" shows now OK instead of YesNo.

Also added copyright header.

Fixes #70: Dialog of windows installer, if software is already installed should show "OK" instead of "yes/no"

Signed-off-by: Marco van Wieringen <marco.van.wieringen@bareos.com>

platforms/win32/winbareos.nsi

@@ -1,4 +1,22 @@
-; Script generated by the HM NIS Edit Script Wizard.
+;
+;   BAREOS?? - Backup Archiving REcovery Open Sourced
+;
+;   Copyright (C) 2012-2013 Bareos GmbH & Co. KG
+;
+;   This program is Free Software; you can redistribute it and/or
+;   modify it under the terms of version three of the GNU Affero General Public
+;   License as published by the Free Software Foundation and included
+;   in the file LICENSE.
+;
+;   This program is distributed in the hope that it will be useful, but
+;   WITHOUT ANY WARRANTY; without even the implied warranty of
+;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+;   Affero General Public License for more details.
+;
+;   You should have received a copy of the GNU Affero General Public License
+;   along with this program; if not, write to the Free Software
+;   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+;   02110-1301, USA.
 
 RequestExecutionLevel admin
 
@@ -435,7 +453,7 @@ Function .onInit
   ReadRegStr $2 ${PRODUCT_UNINST_ROOT_KEY} "${PRODUCT_UNINST_KEY}" "DisplayName"
   ReadRegStr $0 ${PRODUCT_UNINST_ROOT_KEY} "${PRODUCT_UNINST_KEY}" "DisplayVersion"
   StrCmp $2 "" +3
-  MessageBox MB_YESNO|MB_ICONQUESTION "${PRODUCT_NAME} version $0 seems to be already installed on your system.$\r$\n Please uninstall first."
+  MessageBox MB_OK|MB_ICONQUESTION "${PRODUCT_NAME} version $0 seems to be already installed on your system.$\r$\n Please uninstall first."
   Abort