Uninstall Avg antivirus on windows 7

Mats, See posting (https://support.avg.com/answers?id=906b0000000D3QnAAK).
AVG Guru

Tried to uninstall AVG antivirus. Failed.It says "Error 1921. Avg Firewall could not be stopped. Verify that you have privileges to stop system services 0XC0070781.
How do I proceed?

Mats, See posting (https://support.avg.com/answers?id=906b0000000D3QnAAK).
AVG Guru