Hello,
apologies for separate thread - found plenty related topics on Avast causing BSOD - however most of topics raised are having multiple workarounds as like still having access to Windows via Safe Mode or so and none addressed my issue after hours of Googling - therefore believe that FRST scan / individual assistance would be required :(.
In my case upon first reboot after installing Avast Free Antivirus:
- Normal and safe mode boot is interrupted by BSOD - STOP: 0x0000007B - pretty generic event, after Googling a bit found this being identified as - NO BOOT DEVICE FOUND - still Windows is booting up and BSOD thrown during splash logo animation - tried plenty of tools embedded to Hiren’s boot bundle, no error of any sort found on SSD disk, tried to fixmbr, rebuildbcd and all sort of boot related troubleshooting.
- Tried changing SATA Bios value from ‘AHCI’ to ‘Compability’ and in reverse as suggested in few threads - no luck
- Tried to generate minidump / any sort of BSOD dump, no dmp files generated / found tho in /Windows/* structure - tried all options displaying after pressing F8 during boot - last proper configuration / activating debugging etc
- Tried to deactivate all Avast related drivers / services on startup using Hiren’s boot tools - the only change I’ve noticed, safe mode during load fails right after CLASSPNP.sys driver file instead of aswArDisk.sys being last one loaded previously.
- Windows provided Repair tools didn’t helped at all
- Unfortunately no restore images taken previousely
Any thoughts / ideas how to put it to the right tracks ? Would prefer to avoid clean Windows install / restore on file level - laptop is mother-in-law’s belonging, you could imagine that this makes restore as Priority 1 case 
Huge thanks for any feedback on this, appreciate.