i have a wireless network that includes 2 PCs and a dlink wireless router.

Each computer is able to access the internet however both computers are not able to "see" each other despite the fact that they ve been setup up with the same workgroup & SSID

Could this be because the router is not wired to either 1 of the PCs. The only link each PC has to the router is via the wireless adapter

Could i be missing something or does 1 of the PCs have to be wired to the router

In fact you are indeed missing a number of things. The router carries the SSID, not the individual PCs. The SSID has nothing to do with your two computers not seeing one another.
The fact that both PCs are wireless makes no difference in this case...even being wireless still makes them apart of your LAN.
Since you kind of sound new to networking here's a few basic things to try.
1. Make sure the ICF/Windows Firewall (or any other firewall [eg Norton, etc.]) is disabled.
2. Enable file sharing on both your PCs.
3. Ping the other computer's IP and name to make sure its really connected to the network and dns is working properly.
4.Try connecting from one pc to the other pc using its UNC instead of browsing in network neighborhood (eg \\computer)

Good luck!

www.monkonline.tk

not saying this will help but first try here
http://support.microsoft.com/?id=318030 and secondly, i have zonealarm and i had to enter the ip address of computer2 into zonealarm in computer1 and vice versa (i have zonealarm in both computers) before both computers could access each other. its in the firewall section. put the ip address in its trusted zone. your lan address should be already in as long as its enabled through the firewall. check xp's own firewall too. you have to have computer browser and netbios and wireless configuration and all sorts of things enabled in the services section of xp on both computers before the computers can see each other. personally i think microsoft have made it really complicated setting up a network of TWO! computers. i mean, i'm not trying to set up a national defense network am i. just two pokey computers. anyway, thats my gripe.