I purchased Avast Internet Security v6 and installed it on my computer using Windows 7. No problems at all. I installed it on my other computer running Windows 7 and I keep getting an error message that says that "an unauthorized change has been made to windows etc. with an error code of 0xC004D401. I uninstalled Avast using their uninstaller and re-installed Internet Security. But the same thing keeps happening. Why would one system be fine and the other have this problem. Both are running the same Windows 7 OS. How do I correct this?
Welcome to the forum. 
Which version of avast! did you install ??
Have you already rebooted your system ???
It’s version 6. No I have not rebooted the system.
Please reboot and give me the full version# 6.0.xxxx
It’s version 6.0.1289 hope that helps. Oh by the way, thanks for helping.
Are you still getting the error after the reboot ???
If you are, can you attach a screenshot ???