If you are getting updates - you should be fine.
But when I had my kak.worm, it was the registry error that sent me to a pro and I found out I did indeed have a virus.

You are correct - .dat is simply a data file...
and it sounds like you are in the "intermediate" user level like me... we can handle the basics and we undertand the basics... but we have to hire a professional when we need it.
I too have a pc guru that helps me when the "easy, normal stuff" won't work - and Iknow just how far I can go before I'll do something stupid.

But even with virus protection in-place and working correctly, we can STILL get viruses if services like Norton haven't been able to get the dat to you before you get the virus! (and that's where the common sense of not opening things with attachments we aren't expecting comes in... or some of the other safeguards we pratice once we feel we have done everything we can to prevent problems.)

It is that automatic scan that will keep you protected... but I am surprised how many people don't know about it or use it

Thanks for posting... because WE ALL MUST do our best to keep the virus problem out of our computers. Responsible pc owners are like responsible pet owners... keep that puppy vacinated and on a leash and maybe he won't kibble on anyone's bits