I installed the recent version of Ultradefrag, and on first loading the programme, it crashed, leaving this notification:
Application Failure udefrag.exe 126.96.36.199 in ntdll.dll 5.1.2600.6055 at offset 00019af2
Not too important, possibly, as later I had no problem to start and use it.
But as I was asked to post the notificatin here - voilà. Prosit.