I've always used MikTeX as the main LaTeX base to compile/write my *.tex/*.sty/*.cls files, so I downloaded the specific version 2.9.4521-x64 on my first computer (running Windows 7 Professional); and then the file extensions mentioned above were correctly recognized by the OS, as it can be seen inside a generic folder:
There is a difference regarding the file type (tipo=type) LaTeX Class and LaTeX Style that recognizes automatically the derived extensions; and so on my first machine I've had no problems at all.
The problem rised when bought a new computer, same OS, and installed the same version of MikTeX; then when I looked back on the same folder the file extension for class was no more recognized correctly by Windows:
Here the file type that describes a class file is recognized as CLS file, and not LaTeX Class, because I had to manually connect the program that will be able to read the extension, as it can be seen by the different icon appeared in the aforementioned image.
I know it may seem as a not-so-dramatic issue, but I don't know what is causing it, and since there is an image proof surely something must have happened.
EDIT: As karlkoeller suggested, removing the current TeXworks version from the MikTeX distribution and installing a brand new one generates this output:

So it looks like I'm back on where I started.


texworks-configwill be something useful to do. Otherwise, apart from installing antother IDE, what are my possibilities? – TheVal Oct 11 '13 at 21:08