Helping people with computers... one answer at a time.
Making sure your anti-virus program and its definition database are up-to-date is the best way to make sure that it can recognize and remove viruses.
I've been told I have the (fill in the blank) virus, but my anti-virus program doesn't remove it. What do I do?
I get variations of this question a lot. Someone has somehow correctly determined that they have a virus; either by its symptoms or by some other means and yet the anti-virus program that they're running fails to detect the virus, or perhaps detects it but fails to repair it.
It's a race, folks, and sometimes the anti virus-packages aren't in the lead.
The fact is new viruses are being discovered every single day. Anti virus (AV) programs are constantly having to update the list of viruses that they know to look for. The AV software firms are always racing to catch up with the new discoveries. Each time a new virus is found they update their information; typically called "signatures" or "virus definitions database" which then must be downloaded by users of their software.
That's you, by the way. And that's why I, and many others, constantly harp on the fact that you must be running up-to-date virus software. And that means both the latest version of the AV program as well as the virus definitions. You need to be regularly downloading the new virus definitions to stay up-to-date and protected against all the new viruses found every day.
How often is "regularly downloading"? I download every night. I wouldn't feel safe going much longer than a week without getting the latest for my anti-virus software.
It doesn't have to be a burden. In fact, all I've done is configured my anti-virus software to automatically download new virus definitions in the middle of the night when no one is using the computer. It just happens and I rarely have to think about it.
Now all that having been said, unfortunately AV programs aren't perfect. In fact it's turning out to be not uncommon for one AV program to catch infections that another will miss. It shouldn't be that way, and quite frankly I'm not sure why it is that way, but it's reality. That's why, when you know you have a virus and your (up-to-date!) AV software doesn't catch it, I recommend running another package. Many AV software vendors have free trials, or free on-line demos, that server wonderfully as a second-line check.
Finally, occasionally a virus will be detected by an AV program, but cannot be removed by it. Certainly the first thing to try again is another AV program. However sometimes there are technical reasons why removing a virus takes additional work. In such cases you should visit the web site of your AV software publisher and search for specific instructions, or occasionally a downloadable tool, to remove that specific virus. Most of the major AV software publishers provide this service.