I've done all of the above, but when I click on Places>Network>Windows
Network, I get the following error:

UNABLE TO MOUNT LOCATION: Failed to retrieve share list from server.

I'm assuming that this is a problem on the Windows side?

I made sure that FILE AND PRINTER SHARING was turned on, and that the
two folders I wanted were set to share.

Windows can't see my Linux computer either. Maybe it's a gateway/router
problem?