This means that one of the programs you are loading has a registry key assigned to load that .dll on its start-up. The program has told the computer to search for this .dll when the program is loaded, so the computer is alerting you that it cannot find the .dll that it is assigned to look for. This is not necessarily a bad thing; it is just the computer acting how it should, by alerting you to anything that is different than it has been told to do. This is a prime example of the computer being a "slave" to the user, only performing activities it is told to do. As I stated, the computer has been told to check for that .dll by the program, and it has not found it.
I would restart the computer and load each program individually. By this, I mean only load one at a time at a significant interval to narrow down which program is the one causing the alert message. This will help you both figure out where to look for the missing .dll (if it is hidden or otherwise elsewhere on the computer) and how to search more exactly for solutions on Google.
So, there is no .dll on your computer (as far as I can tell), or it is missplaced somewhere on your computer that the program is unfamiliar with. The computer was told to look in an exact place, and the file apparently isn't there. A real-time scan by one of your security programs might have deleted this .dll because it thought it "malicious". I've had my real-time scan do this with some of my "handy" basic programs that were very simple but could be construed as "malicious" by a security program.
...sorry for the long post