On the other hand, under My Computer-Network, both PCs can see each other and access any shared files between the 2.
So it would appear that you do not have a Windows Networking issue.
My suggestion is to check the game forums specific to the games you are using and see if any members may have suggestions for you. Paying particular attention as to how to configure the native Windows firewall as well as any third party Security Suites that may be present on either or both PCs involved, ports and protocols that may be required to be opened with respect to the host (server) machine and the client.
Regards
Randy