Before installing Chrome check that the installation directory doesn't exist (or can be deleted).

chrome/app/google_chrome_strings.grd

Index: chrome/app/google_chrome_strings.grd
diff --git a/chrome/app/google_chrome_strings.grd b/chrome/app/google_chrome_strings.grd
index 747c303a7e1d9c0eda6b0325b151369da7282aff..ac0127b787d6cdcde3c619e35d8beca9b0dacd1f 100644
--- a/chrome/app/google_chrome_strings.grd
+++ b/chrome/app/google_chrome_strings.grd
@@ -305,6 +305,9 @@ Chrome supports. -->
       <message name="IDS_UNINSTALL_FAILED" desc="Error during uninstall if we can not find the installation directory from registry.">
         Google Chrome is not installed or it failed to find installation directory. Please download Google Chrome again.
       </message>
+      <message name="IDS_INSTALL_DIR_IN_USE" desc="Error during install if Google Chrome version is missing from registry but the installation directory exists and can not be deleted.">
+        Google Chrome installation directory seems to be in use. Please reboot your computer and try again.
+      </message>
       <!-- Options Dialog -->
       <message name="IDS_OPTIONS_DISABLE_SERVICES" desc="The text in the options panel that describes how we use web services to improve browsing experience.">
         Google Chrome may use web services to improve your browsing experience - you may optionally disable these services.