I am connected to wireless network but, cannot pull up the internet?

I have a router that connects our desktop and laptop upstairs I just got another desktop and set it up downstairs with a wireless adapter. I got the card connected to our wireless connection but, I cannot get on the internet it says page cannot be displayed. I am running Windows XP SP2 in this new computer and I have check in network connections and it says connected, obtain IP addy automatically is checked, DHCP is enabled in our router and this new computer, I have tried repairing the connection but, that does not good. I did an ipconfig and found it was connected to automatic private address my other two computers say they are assigned by DHCP how do I get this 3rd computer to connect to the internet???? Help!!!!

I am connected to wireless network but, cannot pull up the internet?computer repair

you did not mention anything about the "wireless key" so I would have to assume this is the missing step.

get the key from the router and install it on PC3

if you did that step allready,

I always setup everything wired first. then setup wirelessly second, some router/network adapter combinations require bridgeing. On pc3 bridge wired and wireless connections if nescesary