I installed Avast Internet Security almost 3 weeks ago with manual update setting, but today when i logged in my PC i saw Avast Premier instead of Internet Security, Please help me about this, is someone else is controlling my PC or it was just a mistake ?
(Sorry for my bad english 
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Old version of Avast Internet Security?
Current version of Avast Premier?
Are you the only user of computer?
Latest version of avast internet security and current version of premier and i’m not the only user of my computer but i am the only administrator of my PC.
So you have a limited standard user account(s) for the other users? If you do, then they cannot upgrade or change the avast program without knowing your admin account password.
Or do they know it?
yes they are standard users and they don’t know my password…
Well, it appears likely that admin access by another user other than you is possible as Premier was installed without your explicit consent.
What is missing is the version of Premier. Is it a trial version or full paid version? Is Avast Internet still installed and running at the same time Premier is?
Confusing is this statement:
At the very least, suggest changing your administrator password writing it down and keeping it in a secure place. Consider also removing the standard accounts and other users as the only known way a system change can be made is through your admin account. For that they would need the administrator password.
Installing Premier can only be done with administrative privileges using the admin account. It can’t be done using a standard account unless you’ve changed the Windows UAC prompt from the default settings. If you’ve changed settings from default then you would not be notified a system settings change was about to be made to your system.
Which is not a safe practice to do from a security standpoint.
Are you running Windows Vista?