There are a few basics which have to be in place to be able to share.
First, both pcs have to be in the same workgroup and have different computer names. Check this by right-clicking on My Computer - Properties - Computer Name.
Secondly, file and printer sharing must be enabled on both pcs. Check this in Control Panel - Network Connections - [Network Icon] - Properties.
Thirdly, there must be something to share (a file, folder, drive or printer on each pc).
Finally, the firewall must be configured to allow communication with the IP addresses of the networked pcs.