When everything is setup you should see the PC in the Network Browsing window, or you can connect to it using "Connect to Server". When in Finder, go to Go then to Connect to Server and put in the name of the PC and the folder that you want to connect to. Make sure that it says smb:// in front of where your gonna connect to.
ex. smb://ibmpc/sharedfolder
or you can use the IP address of the PC
ex. smb://192.168.100.2/sharedfolder
I would create a shared folder on the PC to connect to. I don't believe you can just connect to the PC you need to connect to the PC and a shared folder. You can share any folder on the PC including the C drive (Be careful in doing that, especially with wireless). It should prompt you for a username and password. Use the Windows username and password.
On the PC side right click on My computer and then click on Map network drive, put the name or IP address of the Mac and the folder you want to share.
ex. //imac/admin
it should then prompt you for a username and password. Use the Mac username and password.