Never turn off your Anti Virus program to install a program.
The fastest way to infect your system is to turn off your current AV program in order to install another program.
Even if the new program asks you to turn off your protection, don't do it.
I have never come across a legitimate program that wouldn't install while my protection was in force.
If you turn of your antivirus program to install a program, it's the same as turning off your alarm at home when you leave the house.
Don't Do It.