Try --force-uninstall param to see if that fixes installer tests.

chrome/test/mini_installer_test/test.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 "base/platform_thread.h"
 #include "base/win_util.h"
 #include "chrome/installer/util/install_util.h"
 #include "chrome/test/mini_installer_test/mini_installer_test_constants.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #include "chrome_mini_installer.h"
@@ skipping 42 matching lines @@
   installer.OverInstall();
 }
 
 TEST_F(MiniInstallTest, DISABLED_MiniInstallerSystemInstallTest) {
   if (win_util::GetWinVersion() < win_util::WINVERSION_VISTA) {
     ChromeMiniInstaller installer(mini_installer_constants::kSystemInstall);
     installer.Install();
   }
 }
 
-TEST_F(MiniInstallTest, DISABLED_MiniInstallerUserInstallTest) {
+TEST_F(MiniInstallTest, MiniInstallerUserInstallTest) {
   if (win_util::GetWinVersion() < win_util::WINVERSION_VISTA) {
     ChromeMiniInstaller installer(mini_installer_constants::kUserInstall);
     installer.Install();
   }
 }
 
 TEST(InstallUtilTests, MiniInstallTestValidWindowsVersion) {
   // We run the tests on all supported OSes.
   // Make sure the code agrees.
   EXPECT_TRUE(InstallUtil::IsOSSupported());
 }