Firewall: well... the thing is that i made many only tests with the firewall turned off and they all said i was secure.
Did you consider that those test maybe were performed on you ISP's firewall/proxy? Some ISP's hide their network to the outside world (internet). It seems that al traffic comes from one computer (their proxy). But actually, this proxy translates (masks) the IP-addresses of their users PC's to the proxy's IP.
Most security scanning sites show the IP-address of the computer that is scanned. Maybe you should check if the IP is that of your computer. If it is not, then another computer was scanned. So the results of the test relate to the computer with the mentioned IP. This means that the security testresult says nothing about the secureness of your computer.

To the outside world (internet) your PC seems secure (because of the firewall/proxy), but inside your ISP's network you're possibly vulnerable to the attacks of other users on your ISP's network.

and each of them have the drives shared with full access (c:\ d:\)...
It doesn't seem a good idea to me to share your drives on your ISP's network. You mentioned you have your PC's connected with a second NIC, I suggest you only enable file-sharing on this NIC and not on the one that's connected to the internet.