Poster in consumers report:
I would like to provide a notice of a potential problem. I moved to Windows 10 and shortly decided to add AVAST as my antivirus program. After I paid for the software I was given a loading program. This program did not indicate that any restrictions existed with any other programs. The program started and the circle of dots started. After 24 hours, it was still going. I stop the machine and called service. They then told me that they were having trouble with Windows 10 and if I wanted to pay for their expert, an attempt could be made to fix my machine. So I got a recovery disk, which did not work. But, I was able to get a DOS directory list of my machine. All my data was corrupted. No tax info, no pictures, nothing. I had too get a new PC. The basic line is, please check to see if there is any unpublished restrictions before you install, and make sure you back up your data on an external drive/DVD.
and make sure you back up your data on an external drive/DVD.That should be obvious, no matter what problem you have or may have you should have plan for a future worst case scenario
This program did not indicate that any restrictions existed with any other programs.Only "restriction" is with other security software. This is basically the reason (not just for avast but others as well) : http://blog.kaspersky.com/multiple-antivirus-programs-bad-idea/
and called serviceWhat you called was not avast but a third party that only handles a very limited amount of things for avast. https://www.avast.com/total-support
They then told me that they were having trouble with Windows 10Without having "seen" your system and knowing the exact problem, I can only say that Windows 10 does have a lot of problems. Especially when it comes to installing/using other security software than Defender.
But, I was able to get a DOS directory list of my machine.Since Windows 7 there is no DOS anymore on Windows systems.
All my data was corrupted. No tax info, no pictures, nothing.Don't know how you looked at it, but it can be everything was still there in order but the software you used wasn't able to read the filesystem correctly.
I had too get a new PC.Correct me if I'm wrong but I believe you mean that Windows was newly installed. You should have been able to use the recovery partition (or disk) that came with the system.
and make sure you back up your data on an external drive/DVD.Not only before trying to install something, but always. A house can burn down. Keep the backup at least a kilometer away from the system the backup is from.
Personally, I create a image of the drive before installing anything.
Ok, it takes some time.
But if something goes wrong, I can easily go back to the second before I started the install.
“Personally, I create a image of the drive before installing anything.”
You are certainly the excedption to the rule.
We should all have a regular backup schedule but doing an image backup before any new install is going to the extreme. 
Create a W10 USB Recovery Boot stick…you can download from MS since your system is no longer operating.
http://windows.microsoft.com/en-us/windows-8/create-usb-recovery-drive
Once you boot into this USB RE stick you can have options to recover your PC…or at minimum copy your personal files off HDD.
http://windows.microsoft.com/en-us/windows-10/windows-10-recovery-options
[size=10pt][i]Use a recovery drive to restore or reset your PC
If your PC won’t start, you can use a recovery drive to restore from a system restore point or reset your PC. For info on how to create a recovery drive on a working PC, see Create a recovery drive.
If you’re using a recovery drive created on Windows 10:
Connect the recovery drive and turn on your PC.
On the Choose an option screen, select Troubleshoot, and then select an option. If you don’t see the Choose your option screen, your PC might not be set up to boot from a drive. Check your PC manufacturer’s website for info on how to change your PC’s boot order.
Restore from a system restore point by selecting Advanced Options > System Restore. This will remove recently installed apps, drivers, and updates that might be causing your PC problems, but it won’t affect your personal files.
Select Reset this PC and then choose to keep or remove your files. For info on how resetting affects your apps and settings, see the Reset your PC section of this topic.
If resetting doesn’t work, you can also Recover from a drive. This will reinstall Windows 10 (unless your PC came with Windows 8/8.1 and a recovery partition from your PC manufacturer, in which case it’ll reinstall the version of Windows that came with your PC). It’ll also remove your personal files, apps and drivers you installed, and changes you made to settings. [/i][/size]