I started with the simplest approach and did a reboot - is there any problem for which reboot is not the answer?. The megafile was still there. However, this time when I tried to delete it the message was "file too large for the recycle bin, do you want to delete permanently". To which the answer was yes please, please, please, and now it is gone! Thanks for the guidance. Niall
I ran wipe free space on my 1 terabyte drive and left it to run overnight. Next day the computer told me that the hard drive was dangerously low on space. This was due to a new file of 795G that appears to have been created overnight by CCCleaner - the name is a long string of letters and digits ending in .rar . It cannot be deleted - access denied. How can I get rid of it and what caused it?