Relatively speaking it is trivial to share files between two windows based system however, things could get complicated if the two systems are running different operating systems.
The minimum requirements are as follows:
* Network connectivity must be established between the two
* You can use wireless or hardwired cables to meet the network
* When choosing the hardwired option, if a hub is not available
you will need a crossover cat 5 cable to eliminate the need for
a hub or switch to connect the two computers.
* The computers must run a network protocol such as tcp/ip
The link below provides bullet proof details on configuring/troubleshooting windows file sharing.