Could not uninstall

[REDACTED]

So I have Avast Business Security version 2015.10.2.2505 installed.
During my update to windows 10 about 1 month ago, the update failed and I'm forced to roll back to Windows 7. Current OS is Windows 7 64-bit SP1.

However, after the rollback, I'm stuck with a non-functioning avast antivirus that:
1. Does not and cannot update.
2. Does not start antivirus service.
3. Does not save settings. (I disabled the self defense module in hope of killing the process but to no avail.)
4. Interferes with my msconfig. (I tried disabling avast during startup but no use.)

So I wanted to uninstall the antivirus and reinstall it again.
But I've tried:
1. Using the business security setup in attempt to reinstall the antivirus.
2. Going into safe mode and running "avastclear.exe".
3. Going into control panel to uninstall the antivirus.

But the thing is that it keeps on coming out with this error:

instup.exe - Application Error
The exception unknown software exception (0xc06d007e) occurred in the application at location 0x7689c42d.

Help? 

[Eddy]

Remove it the old fashion way > Manually.
- Remove all folders/files related to avast
- Remove all registry entries pointing to avast
- Reboot.

[REDACTED]

It doesn't say where the instup.exe is being started from or when. 

It could be in a Windows startup somewhere trying to resume an install, in which case it might be located in %USERPROFILE%\appdata\local\temp according to http://www.freefixer.com/library/file/instup.exe-105880/

As a thought, Try doing a Disk Cleanup to delete temp files or maybe safe mode to delete temp files in this location. Reboot and run avastclear.exe in Safe mode once again to be sure.

[.: Mac :.]

aswclear works on the business versions:
https://www.avast.com/uninstall-utility

[REDACTED]

aswclear works on the business versions:
https://www.avast.com/uninstall-utility

As I said, it does not in my case.