The scan of my system just completed.
I will report back with a bit more information on space occupied etc.
So my scan took about 33 minutes. My system is a dual processor (2 X 2.8GHz) with 2Gb RAM.
A bit more detail ... of my 900Gb about 460Gb is occupied.
But I want to be truthful and report that the majority of the time was (due to the exclusion list I have created in avast) spent on my C: drive.
My C: drive (internal SATA) has 18Gb occupancy. Of this 18Gb 2Gb is used by the hyberfil.sys (hibernation file of Windows and in my exclusion list) and another 8Gb is used by Goback (unfortunately now owned by Symantec) that allows me to revert my system to any point within 30 seconds or so within the last two weeks and allows me to understand a lot of what avast is up to - this is also in the avast exclusion list.
My second internal drive (SATA) has a partition that is scanned by avast but has only about 2Gb occupancy.
The other three drives are external USB. They are scanned by avast but contain mainly files that I have decided avast need not scan (they are in my exclusion list). They are mainly .jpg, .mp3, .flac, .avi, .mpg, .wmv, .tivo (files uploaded from my digital video recorder), .tib (Acronis True Image backup).
I could probably save even more time by preventing avast from scanning my Thunderbird archive folders - since avast does not understand them - but they are only about 500Mb in total.
So what's the bottom line for me?
I'm probably being a bit unkind to avast in my estimates but it is taking avast about 30 minutes to scan about 10GB of data thoroughly including all the archive files on my system drive (it is probably rather more data if I counted the files on all the disks not in the exclusion list).
So, how much data have you got taking more than 9 hours?