Dave CCleaner:
Can you recall which 5.4x version you were updating from? Was this in response to an in-product notification advising that you were 11/12/13 released out of date?
Possibly 5.44 but I'm not sure. There was a reminder that there was a newer version to download. I usually ignore those because they just tend to add bloat that I don't use.
At what point did Trend Micro pop up during the first failed install attempt? Do you recall what it said when it did pop up?
During the installation the progress bar was perhaps 1/3 to 1/2 across. I think TM's message was to the effect the the installer was doing a DLL modification or injection. The options were to allow once or block once and it said something like 'If you don't press anything the action will be allowed in 30 seconds'. There were 2 of those - and then the installation hung.
At what point did the CCleaner installation show as unresponsive in the Task Manager? Was the failure to delete the old CCleaner executable something you observed, or was there a specific error message that popped up telling you that it had happened?
I don't remember the exact details of what happened. There was a message about being unable to delete the executable. I triedreinstalling a couple of times andwhen I opened the task manager there were multiple CCleaner processes running - without any visible ccleaner windows.
The PC may have been, as you say, a dozen releases out if date - that's exactly why I turn off the auto-update and the auto notifications and the auto-monitoring and the auto-phone-home and the rest. Ccleaner was great for me a couple of years ago and all the new 'features' that are being added take away from its utility.. I don't want it running background processes, I don't want the idiot mode, or the dumbed down report etc.
I'll keep an eye out and let you know more details if it happens again.