Computer able to ping by IP and host-name but not visual in browser

I exported the services list of the strange computer and filtered it based on stopped services. I did that in order to try a Vlookup between the services on both computers. When I tried to do the same thing on the good (seen) computer I could see the strange one in the network and could connect to its shared folders...
I did not do anything else but changing its IP. Five minutes after this change (computer reboot, router reboot) it used to behave also strange like I described in the initial post.
Now it behaves normally, everybody can see it in the browse window and access its shared folders.

I do not have an explanation for that...
Anyhow Thanks GokAy for that idea of IP changing. Even if I cannot understand how this change solved the problem...
Any idea regarding WHY?

GokAy said:

Yeah, comp name too indeed :)

Does it show on the other router? Maybe the answer is in the router and not the PC.

It used not to be seen even from computers connected to the same router. And all the other computer connected to the same router could be seen from all routers...

Did you change the IP to a known working one, or another unassigned IP? Unlikely but maybe you had a duplicate IP? Should have had issues if this was the case though. Maybe listed in Event Viewer.

I changed its IP to another unassigned one.
If we would have an IP conflict I think that a message announcing that should be received. Even if only the message was missing how can we explain the fact that it worked well (with the same IP) being connected to the main router?