All of the above recommendations have already been implemented as can be seen from the pictures I have linked to.
All of the computers on my LAN diagram are on the same subnet (192.168.1._). Only other subnets are Opt1 (192.168.2._) which is the unused nic on the gateway and 192.168.10._ which is the WAN on the wireless router (the connection that is also unused).
NetBios is enabled on the Win7 box (wireless), don't know how to tell on the XP box (wired). Trying to see shares from under identical User Name accounts on both computers made no difference (account passwords were disabled on both).
Currently, both the WinXP and the Win7 comps can ping each other without any data loss. Therefore, data flows either way and the issue seems to be only OS related. The XP box sees 7's shares but 7 doesn't see XP's OR its own shares (in the Network section), nor does 7 see any computers on the network including self.
The tutorial link suggested covers an example of sharing btw W7 64bit and WinXP sp3. My W7 is 32bit and XP is sp2. Further, I do not wish to apply the sp3 patch. Every other step in the tutorial has been followed exactly. If you happen to know that the problem resides on the XP end, please advise if it can be fixed with a particular small patch (as a specific subcomponent of XP's sp3 package, for example). However, it seems unlikely that XP is at fault since 7 cannot even see itself.