Windows 8 networking changed a lot. Gone are some simple shares and the version of Windows 8 matters now.
There are too many reasons for this to fail such as the firewall in the router or any of the computers. I'm finding new consumers that will not turn off the router firewall so we have to tell them it doesn't work and show them it working on our router (if they pay!) where we turned it off.
This may be good news for tech support companies.
Neither Apple Support nor Dell Gold Support can diagnose problem. Gigabit network linking both machines and two other Dell machines. IMAC can "see" two Dell machines' files but not high-end T7500 work station running Windows 8.