[color:"orange"]dual core 1.86GHz processor(s). Now I wonder: is this equal to a 3.72GHz processor or is it just faster then a 1.86GHz processor?[/color]

It depends on the program. Most current programs are not multi-threaded, so would only be able to use one core. However, Windows can manage which applications are run on which core, so if you have multiple programs running, task switching would be smoother (ie a CPU intensive program running in the background would not interfere with whatever is running in the foreground, and vise versa).

Some programs are multi-threaded, particularly CPU intensive ones such as video editors, etc, as are a couple games, so would be able to utilize both cores at the same time. It depends on the program on how much of a difference that would make; there is a little overhead managing the 2 cores, so at a maximum you would get a bit less than 3.72GHz performance out of any program.

Multi-core processors are the way Intel and AMD are going, so eventually multi-threaded applications should become more common (for non-trivial applications, anyway).