Firewall software

Hi. I am a newbie and this is my first post.

I hope I am in the right place

I have a DSL connection with Virus Scan that is activated every time my system boots. All of a sudden the other day I get this message when I connect to the net that says "STOP" is your computer getting hit with popups, slower, crashing, etc.???

I was wondering if anyone can help me figure out to get rid of this stuff and if I need a firewall (I am not sure I have one).

TIA.

 

the box that pops up with this message. Does it say "Messenger Service" in the blue bar at top of the window?

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