Please download to your desktop
MBAM (click on the blue download button).
After it is downloaded double click the file to install it. This will take a minute or two.
Once installed, run it, update it, and perform a quick scan.
Place a check mark in each box for anything found, and press "remove selected".
You can not connect a Windows computer to the internet, even for a minute, without antivirus protection, or the chances of infection are quite high.
You should also check that the firewall is turned on.
Let us know what you want to do.
If you choose to use Avast and remove McAfee, there is a removal too for McAfee, too.