No offense pwnzer, so don't take me wrong, I'm saying this to help you.
Count all anti-viruses as super-ego's..
I mean, compare all programs like different OT's, they are all good at something, but none of them are good at everything.. but they're too ego, to help each other.
So one anti-virus may be super nice! but it doesn't know everything.
There are new viruses daily, and the anti-viruses are ALWAYS one step behind no matter what.
Someone must find the virus, and tell the developer of the anti-virus about this new virus so they can add it to their database, but before someone detect it.... nothing will scan it as a virus... because it's not yet known.
Those who are noobs and want to spread viruses, those are the ones that always get stuck at scans, because they leech stuffs that other release, and when something gets released, the scans will know about it(maybe not all but most)
The dangerous ones, are those who make their own viruses from scratch, then there's nobody that can know for certain, that there's a virus in it.
And viruses isn't some magical thing.. it's simple codes, most written in C++, to do things it's being ordered to do on your computer..
Sure there's programs that can detect odd behavior in computers (viruses moving around), but that can never be dead certain, because if they really could detect everything with those detections, that would be you'd get 1 new warning every 5 minutes while you're at your computer.
Because windows is constantly doing new tasks and they look similar to what viruses does.
They run a code, check for updates, maybe keep an URL clock going by getting timestamps from microsoft, your flash player is loading something to check if there's something new.. your other programs, checking for updates and stuffs..
constantly..
to summon up.
For an antivirus to detect a virus (ONE virus), it need to know that virus is a virus from the developers to be certain.
But until the developers find the virus, you will scan it as dead clean
yeyeye, I know, I just wrote a book..... big deal.......