Update to the latest version (12.1.2272): https://forum.avast.com/index.php?topic=187663.0
Asyn - In this latest version (12.1.2272), there is no longer any reference to Enable Hardware-Assisted Virtualization. Why so? What is happening? No more NG?
You are right.No more NG. 
Topic was dead for a year.
I wonder if antiknijn is using a 2015 version or a newer one…
My Avast just upgraded to 12.1.2272 and guess what - hardware-assisted virtualisation stopped working !
The “Hardware-assisted Virtualization” checkbox in Avast Settings → Troubleshooting has been removed as well - great !
Tried disabling “Cyber Capture” and rebooting, but did not work …
Any alternative anti virus software out there that works fine with HAV ?
Tom - It remains a mystery to me what NG or Avast’s virtualization ever did. It is also a mystery what “Cyber Capture” does. It is also a mystery whether (for Avast AV Free), there is now ANY sandboxing or use of virtualization. And it is a mystery whether or not Avast Free protects from ransomware.
Nothing is explained here. But the updates cause problems, in this and other areas.
Avast spends a lot of effort in designing annoying pop-ups that are the direct opposite of the purpose of their product. In the news, Avast is looking to buy AVG, so that is the corporate focus, not the quality of this product.
I stopped recommending Avast to friends and colleagues. I would be embarrassed to inflict these annoyances on them. Although I still use Avast on my old XP and Win 7 machines, in my Windows 10 machine, I did NOT install Avast, as Windows Defender is working and is nice and quiet and reliable.
Really too bad. Avast was great for a long time.
Asyn - thanks for link. But what does it mean? What is that other thread talking about?
The devs removed the option in the settings “unintentionally”.
As workaround you can tweak the registry, as pointed out by pk.
I just ran into this problem the other day with the new version of Avast.
“Nox App Player” would not open and I was puling my hair out trying to figure out how to fix this issue. Past Avast versions had the Hardware-Assisted Virtualization setting which when I disabled it would allow Nox App Player to run. But now that Hardware-Assisted Virtualization setting was removed I was going insane. Luckily the registry hack works.
Is Avast planning to add back the Hardware-Assisted Virtualization setting any time soon?
Users who use software like Nox App Player should absolutely not need to hack their registry to get it to open properly.
Avast needs to fix this ASAP 
Use the work around to disable avast virtualisation as mentioned by pk.
Can I +1 a need for a solution for this? I’m a software engineer and I’m sure the Avast devs can relate to this. The inability to easily tell Avast to let me use Hardware virtualisation is seriously blocking me from important work-related dev tasks.
I just started a new project for a client where I need to write an Android application, I’ve installed a new version of Android Studio and I cannot launch any virtual Android devices because according to Android Studio the HAV features of my machine are off. They are on, and I already have and use Virtual Box occasionally for some Linux dev work on my Windows dev machine.
It’s bloody stupid that we have to fight with the Avast software to do something we need. This is making me regret my purchase of the product, and when it comes to renewal time I’ll be seriously considering competing products… if I haven’t given up and switched already by then.
EDIT: This isn’t a fault with Android Studio, but Avast blocking access. I did have this issue fixed a month ago but the Avast application has updated I see and reenabled features I had switched off, and now seem to be unable to repeat the steps to get full control of virtualisation again
The problem is not only with avast.
The problem is with many VM’s that are trying to use the hardware virtualisation at the same time.
Here we are six months later, and the new version of Avast is doing this again. Avast 17.1.2286
ONCE AGAIN, AVAST’S “ENABLE HARDWARE-ASSISTED VIRTUALIZATION” STOPS WINDOWS VIRTUAL PC - XP MODE FROM WORKING IN WIN 7 PRO 64-BIT.
When I turn off Avast’s “Enable Hardware-Assisted Virtualization” in troubleshooting, XP Mode starts working again.
Avast, you really are off the rails. Thank God we don’t need you for Win 10.
What CPU do you have? Did you install Avast first, or XP mode first?
It is also doing this in windows 10 64bit i5-6600 cpu
igor -
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Dell Optiplex 7010 Mini-Tower, now with 16GB RAM, two 500GB hard drives and an Intel Core i5-3470 CPU @ 3.20GHz - dual-booting Win 7 Pro 64-bit and Win 10 Pro 64-bit. Avast is on the Win 7 side only.
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Two and a half years ago, when I first got the machine, I probably installed Avast Free before I turned on anything else. This problem - Avast taking over the entire virtualization capacity and blocking anything else that requires virtualization - first appeared shortly after I got the machine in late 2014, per the beginning of this thread. Some time in 2015, a new version of Avast stopped the problem. But now it’s back.
This is now an old problem with Avast. You were aware of it before and fixed the conflict. Time to do so again, and please don’t forget the issue going forward.
No AV should reduce or block the capacity of the machine. Virtualization is not there only for Avast. As you can see from the post immediately above, I’m not the only one affected. Thanks.
Hi, are there any errors in event log? (Application and Services Logs/Microsoft/Windows/Virtual PC/Admin)
Also what version c:\Windows\System32\drivers\vpcvmm.sys file has?
I can confirm that with that option enabled by default, my VM ran much much slower, UI was slowly rendered. Switched off the option in troubleshoting → reboot → the VM worked flawlessly again like nothing happened
Please fix it. We don’t want to uncheck that option but we have to do so to regain the speed of other apps