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

chrome/app/chromium_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- This file contains definitions of strings that are distribution specific.
 These strings will not be translated and only english versions will
 be available for now. -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/chromium_strings.h" type="rc_header">
       <emit emit_type='prepend'></emit>
@@ skipping 239 matching lines @@
       </message>
       <message name="IDS_INSTALL_INSUFFICIENT_RIGHTS" desc="Error displayed when a non admin user tries to attempt system level install/uninstall.">
         You do not have appropriate rights for system-level install. Try running the installer again as Administrator.
       </message>
       <message name="IDS_INSTALL_APP_CONFLICT" desc="Error displayed if installation fails due to another existing application.">
         A conflict with another installed application has been detected.
       </message>
       <message name="IDS_UNINSTALL_FAILED" desc="Error during uninstall if we can not find the installation directory from registry.">
         Chromium is not installed or it failed to find installation directory. Please download Chromium again.
       </message>
+      <message name="IDS_INSTALL_DIR_IN_USE" desc="Error during install if Chromium version is missing from registry but the installation directory exists and can not be deleted.">
+        Chromium 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.">
         Chromium may use web services to improve your browsing experience - you may optionally disable these services.
       </message>
       <message name="IDS_IMPORT_BOOKMARKS" desc="Explanatory text for the importing progress dialog when importing a bookmarks.html file from the bookmark manager">
         Chromium is now importing Favorites/Bookmarks.
       </message>
       <message name="IDS_START_IN_PROFILE_SHORTCUT_NAME" desc="Name of the desktop shortcut to start the application in a specific profile.">
         Chromium for <ph name="profile_name">$1</ph>
       </message>
       <message name="IDS_OEM_MAIN_SHORTCUT_NAME" desc="Name of the desktop shortcut to start the application for OEM pre-installations.">
         Internet Browser
       </message>
       <message name="IDS_SHORTCUT_TOOLTIP" desc="Text for the hover-on tooltip for the Chromium shortcuts.">
         Access the Internet
       </message>
     </messages>
   </release>
 </grit>