Formatting the machine is a rather harsh step to take for a network problem (even a windows network problem). The system is obviously not having hardware issues. Well, this could happen from a bad NIC, but that’s rather rare – especially if TCP/IP is still working properly – which it is.
Your problem is specifically with the domain or workgroup that you’re supposed to be a member of. Check the netwrok settings on an operational system and make sure the problem system has the same settings. If it doesn’t change it. If it does, remove the system from the domain and rejoin it.
No need to bring out the shotgun to kill the mosquito 🙂