Fix stupid mistake of forgetting negation in if condition.

chrome/installer/setup/main.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <string>
 #include <windows.h>
 #include <msi.h>
 #include <shlobj.h>
 
 #include "base/at_exit.h"
@@ skipping 308 matching lines @@
                               installer_util::SYSTEM_LEVEL_INSTALL_EXISTS;
     int str_id = system_install ? IDS_INSTALL_USER_LEVEL_EXISTS_BASE :
                                   IDS_INSTALL_SYSTEM_LEVEL_EXISTS_BASE;
     InstallUtil::WriteInstallerResult(system_install, status, str_id, NULL);
     return false;
   }
 
   // If no previous installation of Chrome, make sure installation directory
   // either does not exist or can be deleted (i.e. is not locked by some other
   // process).
-  if (installed_version) {
+  if (!installed_version) {
     std::wstring install_path(installer::GetChromeInstallPath(system_install));
     if (file_util::PathExists(install_path) &&
         !file_util::Delete(install_path, true)) {
       LOG(ERROR) << "Installation directory " << install_path
                  << " exists and can not be deleted.";
       status = installer_util::INSTALL_DIR_IN_USE;
       int str_id = IDS_INSTALL_DIR_IN_USE_BASE;
       InstallUtil::WriteInstallerResult(system_install, status, str_id, NULL);
       return false;
     }
@@ skipping 263 matching lines @@
   } else {
     install_status = InstallChrome(parsed_command_line,
                                    installed_version.get(),
                                    options);
   }
 
   CoUninitialize();
   BrowserDistribution* dist = BrowserDistribution::GetDistribution();
   return dist->GetInstallReturnCode(install_status);
 }