Catch a virus? Why does it say this?

I have a virus protection software called AVAST! antivirus...I never got a virus since january 17 2013

I have a thing called PS VITA...it said that I need a thing called Content-Manager-Assistant...

I wanna know if you get a virus and I have avast! Anti virus software

I don't wanna damage my computer so please be honest and tell me (I have windows7)

I ALSO wanna know why does it say 

DO YOU WANT TO ALLOW THE FOLLOWING PROGRAM TO MAKE CHANGES ON THIS COMPUTER?

This part got me scared so I wanna know why does it say this an if I will catch a virus.

I think you are using the Avast free edition of antivirus, you need to know one thing that this type of any free edition software's has the limited features in terms of security.

Do one thing that uninstall the avast antivirus and some sort of malware programmes are installed on your computer. First go to control panel and add/remove programmes uninstall the unnecessary software's and other things that you dont need.

After uninstall the Avast free antivirus, download the Norton internet security and ccleaner, Trojan remover. Install the trojan remover and reset the windows policies, internet explorer policies...etc and scan the whole computer and follow the on screen instruction. Troaj remover will clean your system, if any trojans were found on your computer.

After install the Norton Internet Security and scan the whole computer, before scanning update the virus definition. They will provide you the 30 days trial version of softwares. If you are impressed during the trial period of Norton Internet Security buy the full version. I assure you it will perform good.