Using W8. I set it, restart computer, and scan starts. I may come back next morning. I find the computer off. Turn on, check Avast log. It does not show this scan in history. I have no idea if it found anything.
Prior to W8, after scanning it would restart and wait there for me to log in, it worked alright.
Now what it seems to do is when I start the computer it thinks it’s supposed to do the boot scan again, then it scans no files but produces this as the scan history. Pic enclosed.
Free, but I’ve bought premium some years. Always latest. Prior to W8.0 (64-bit) it was Avast too as I recall. Way back I used AVG. No other AV is enabled.
First, be sure to get rid of all remnants of any prior installed AV(s)…!!
→ https://support.avast.com/article/11/
Then:
I can’t believe there’s anything wrong with my installation and I’m not inclined to do all that work right away. I need more feedback.
I presume it’s an Avast imperfection. Do you know cases where the boot scan works right in W8? What does it do after it finishes, compared to mine? What do your tests do? Remember it is preboot so how could my other installations be a cause?
There’s a report file (in case anything was detected) in C:\ProgramData\AVAST Software\Avast\report\aswBoot.txt, plus there’s a log file (C:\ProgramData\AVAST Software\Avast\log\aswBoot.log).
Hello ygslvn, I spent more than 2hrs by trying to induce the issue you have and the only way I induced the same result from the boot time scan was when I interrupted the scan by turning the machine off. Which I do not assume is your case, although it could be - like to computer, for some reason, turn off itself after a while of scanning. In such a case, you will see the scan was started at some date/time but running 0 seconds, tested files 0 etc. as it creates the rest of the report after it is done. Also, it could be, the scan crashed for some reason. In both cases - turning the machine off or scan crash, it will result in what you see in scan results.
So, the most useful will be to get a support package from you so we can look at the log files (especially the one mentioned by my colleague Igor) what happened on your machine. There can be a bug in the product we can fix 
The support tool can be found on our website (https://support.avast.com/en-in/article/Submit-support-file) or in the program folder of the AV (e.g. “c:\Program Files\AVAST Software\Avast\SupportTool.exe”) - just run it, fill the email, send it and let me know the name of the package so I can look at it. Thank you for your cooperation!
Support file is sent. UIZ1Y.
Would be good to hear testimony from others that it does work right.
Hi ygslvn, thank you for the support package. We have looked at it with Igor and found out, few times mentioned (on this forum), errors in the report file Error 0xC000009C {STATUS_DEVICE_DATA_ERROR} for several files on your drive. There are only two things we figured out it may cause this problem. One is a problem with disc/filesystem, second could be a raw access to the drive used by boot time scanner.
So, please try the following and let us know, if it helps:
1/ Start → type “cmd” → right click on Command prompt → execute as administrator → type “chkdsk c: /scan” (eventually, execute “chkdsk /r” but in this case, backup your files as scan and fix operation may “corrupt” something during the fixing process).
2/ Open Avast Antivirus → Menu → Settings → Search → type “geek:area” → click on the searched item → find “Enable raw disk access during Avast Boot-time Scan” option - it is in Scan section there and untick the checkbox.
You can try both of the things in oposite order and one-by-one - maybe good to start with the second one as it is kind of easier and safer. Please let us know the result.
Regarding the data errors, those items were imported from external media and previous systems into my W8 drive. I’m not concerned, those files appear to be usable.
I can’t do chkdsk because that Start is not in W8.0. I checked C via Properties panel and no problems. Is that the same thing?
Overnight I redid boot scan with raw access off, and got same behaviour. Enclosing report which shows nothing.
What is Avast supposed to do when it finishes boot scan.
Chkdsk has been around way before Windows 8
I take it that staff is going to leave the program as it is?
See Reply #8 from Petr.