reset password on my computer

Hi, I am new here. I have a problem with the avast program on my computer. I would appreciate some help please! I already submitted a ticket to support but no-one has responded.

A guy in his computer repair shop called Computer Geek, installed the avast program on my computer when it was in for repair. He has since gone out of business. When he installed it he set up a password to access the commands which he did not share with me. I need to be able to access the commands myself so I can download a program I trust but which Avast keeps blocking. I cannot shut the shield control off temporarily. There is no way for me to find out what he inputted. How can I get this information so that I can set up my own password - which I will know?

Can anyone help or advise me on this?

Which avast!..?? (Free/Pro/IS/Premier)

Hi, and thanks so much for responding. This is the info.
avast! Free Antivirus
program version 2014.9.0.2006
virus definitions version 131222-0
It just keeps updating itself and running but I can’t do anything because of the password he put in.
My computer is a PC with windows 7

If you dont have avast password, there is only one solution

Remove with avast removal tool. http://www.avast.com/en-eu/uninstall-utility

Then reinstall. http://www.avast.com/en-eu/download-software