Avast for Business breaks Windows 10 startup (2nd PC now)

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The first time this happened, I thought it was just bad luck as I have a ton of apps on my desktop Lenovo PC with Windows 10. When Avast asks to restart, upon installation, kiss your PC good bye. Whatever it does, it breaks startup process. Windows 10 won't start. It's so bad that even restore point can't complete, but luckily even though restore point says it failed it did remove Avast and restore it to previous state.

Now, I got a new Toshiba laptop with Windows 10. Put Avast for Business on it, worked fine until I was ready to restart it. Guess what happened? It kept giving me error message that Windows did not restart correctly and needed to be restarted or you had to use advance options. Restarting, shutting off kept throwing the same message. Wouldn't start Windows 10. Had to again resort to a restore point, and again it said it failed. But restarting laptop worked this time and restore was successful, Avast gone.

I'm afraid of installing it again. I managed to get Lenovo to work, so maybe laptop will work again. But there's definitely a bug of some sort, first time might be bad luck. Second time on a completely brand new PC? It's not luck.

I'll try installing one more time, if it breaks my laptop again I'm leaving Avast for Business and Avast. Don't need extra work, last time wasted a whole day trying to get back into my PC.

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It does sound like bad luck   

Can you try downloading the installer again?  It sounds like maybe it is corrupt somehow.  Go to add new device in the cloud, from there choose "Download this installer onto this device" and select customise installer.  I use the Full and Interactive installer.  Compare the new download to the old (file size is a big hint your original is bad). 

Alternatively try installing to a snapshotted Virtual Machine or other non-essential machine just to check before committing to production.  You should get into the practice of doing test installs of any new products that installs a driver or service, or having a full disk image handy just in case you can't depend on Windows repairs.   

Also verify you don't have any "trial" antivirus products installed on the factory image that might conflict.

[Eddy]

Just saying something is not working (correctly) isn't much to go on.
What exact avast version ?
Is (or was) there any other security (related) software on the system ?
etc..

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I uninstalled Avast for Business yesterday, on Win 7 Enterprise, and the OS didn't boot anymore. Whatever it did, couldn't be repaired with "boot repair", and not even following several manual procedures i found on the net.