Solved Could Windows Update force my antivirus to upgrade

Hello,
for two days, the 'Definition Update for Windows Defender - KB2267602 (Definition 1.193.1923.0)' appeared among the important update, I tried to installed it twice, it failed, then I troubleshooted it, but the same result, too.
After a while, the same update appeared but in a newer version 'Definition Update for Windows Defender - KB2267602 (Definition 1.193.2004.0)', I tried to install it and it didn't work either.
to my surprise, my Avast Internet Security 2015 was updating itself to Avast Premier.
I didn't understand any thing, but I think it has to do with the 'Definition Update for Windows Defender - KB2267602 (Definition 1.193.2004.0)'.
any explanations or suggestions, please?

Windows Update cannot force Avast to update itself, only Avast can. Is Avast running?

Agreed, Updates are usually only for Windows and other Microsoft programs such as Office and Windows Defender. What Avast! seems to be doing is Upgrading you to a better[?] version and usually a user has to interact with such a message offering the Upgrade for it to happen.

Some software programs when installed have the option to automatically update to newest version if available. Generally this means newer versions as long as there is no change in subscription costs for the user. Personally, whenever I see this option I always decline because I want to be the only one that changes anything. Same with Windows updates which I have set to notify me but never download and install automatically.

Avast is running perfectly, but it's really weird for me.
now, I tried to open Chrome (the latest stable version) but it closes itself, I can only open it in the Guest mode in desktop mode!!

NourinE said:

Avast is running perfectly, but it's really weird for me.
now, I tried to open Chrome (the latest stable version) but it closes itself, I can only open it in the Guest mode in desktop mode!!

Click to expand...

If Chrome is your only browser I would download and install Firefox so you still have browser capabilities then uninstall/reinstall Chrome and see if it still malfunctions. I say Firefox because it is a very easy install and very easy to use if you have never used it.

I had used Internet Explorer before I moved to Mozilla for a while, then I tried Chrome.

I reinstalled Avast Internet Security 2015 and now it works fine. I have doubt about a Windows Update 'Windows Malicious Software Removal Tool for Windows 8, 8.1 and Windows Server 2012, 2012 R2 x64 Edition - March 2015 (KB890830)'
is necessary to install? it appears in Optional Updates.

I installed the update and does no harm.

I installed it without any problem, too.
I think the problem is Avast Premier, it crashed right after two boots of the upgrade.
no Chrome works fine.
thank you all.