Fix relaunch of Windows Explorer

https://bugs.launchpad.net/bleachbit/+bug/1571440 reported by
ROCKNROLLKID
https://bugs.launchpad.net/bleachbit/+bug/1596195 reported by TW Burger

cleaners/windows_explorer.xml

@@ -81,6 +81,8 @@
     <warning>This will restart Windows Explorer.</warning>
     <action command="process" cmd="taskkill.exe /f /IM explorer.exe"/>
     <action command="delete" search="glob" path="$LOCALAPPDATA\Microsoft\Windows\Explorer\thumbcache*.db"/>
-    <action command="process" cmd="cmd.exe /c start explorer.exe"/>
+    <!-- On 64-bit Windows, it is important to start the 64-bit Windows Explorer,
+         so use the full path. Also, do not wait for the process to terminate. -->
+    <action command="process" wait="false" cmd="%WINDIR%\explorer.exe"/>
   </option>
 </cleaner>