Here is the cursory checklist.
1. Disable the windows firewall on all machines (or configure it to allow the netbios protocol as an exception), or if you insist, configure your firewall permissions to allow netbios traffic to and from the box.
2. Make sure all your machines are on the same workgroup (it isn't case sensitive but you can never be to sure, sometimes if you sneeze at it wrong it stops working).
you can change this by My Computer >(right click)>Properties>Computer Name>Change...
WORKGROUP is the default so that is fine.
while you're at it give the computer a simple, easy to remember name.
3. Reboot all the machines you've changed configs on.
4. Create a share
5. See if you can access it from a different machine.
TROUBLESHOOTING.
If you can't browse shares:
First:
Try pinging all the other clients to make sure your computer can see them "ping COMPUTERNAME (the one i told you to make easy to remember) or if you have static ip addresses you can just ping those (192.168.###.###). If you can't ping all the other clients either you have a router filtering ICMP or a network configuration problem, which you'll have to look elsewhere to resolve.
The other common problem is that a machine just doesn't want to "play nice" as the master browser. Symptoms of this are when you add a new machine to the network everything stops working. (you try to browse the network and explorer soft locks), you should still be able to browse machines by their internal ip though, the syntax for this is \\<internal ip>, so for example one of my machines has the ip 192.168.0.166, if i wanted to browse what services/shares it is offering I would just open an explorer window and type \\192.168.0.166 in the address bar. The solution to this is disabling the computer browser service on the offending machine. start>run>services.msc>Computer browser>right click>properties>disable, stop, ok
Another thing I would advise against is mapping shares that aren't always available, a lot of times explorer will hang if you try to browse these unavailable shares, or even just opening the file browser will be enough to cause it to hang.
In my experience these two caveats cause 99.9% of the headaches with simple windows home networks.