If the box was checked, then that was why you were getting the “unable to find a certificate to log you on to the network” message because Windows is looking for one, but your wireless router is not setup for certificate security. " From: Upgrade to SP3 and you should be able to connect to your network.
The below guide has been tested on MS Windows XP Professional and is based on Windows' default wireless configuration tool (Wireless Zero Configuration).
It Can Find The Network Fine, But When I Try To Connect, I Don't Get The Password Prompt -- It Moves Straight To Validating Identity, Scans, And Then Says Was Not Able To Find A Certificate To Log You On To The Wireless Network Foo.
Click on Properties once you select the wireless network that is having problems. I know it says for IT professionals but it will work for what you want to do. id=24 If Windows XP is already installed there is no need to boot via USB to install SP3. Simply download the file Windows XP-KB936929-SP3-x86from the Microsoft site. take it to the computer in question and click on it.
Click on the Authentication tab and now uncheck the Enable IEEE 802.1x authentication for this network box.
error "windows was unable to find certificate to log on to the network" & showing validating identity.
i tried unchecking the enable authentication box under advanced settings but still no result.
Found this; "Try the following: First, click on the wireless icon in your taskbar and under Related Tasks, choose Change advanced settings. I just use a disc slip-streamed with a computers drivers. But if neither wired nor wireless works them you may have to bite the bullet.
Now click on the Wireless Networks tab and select the network in the list at the bottom. For Windows XP you do not need to boot from a USB drive. I have worked long hours on problems like this which only resulted in a System Reload to solve it. In order to configure the connection back to Automatic, edit the eduroam profile, go to the Connection tab and check Connect when this network is in range: Figure 14: Setting Automatic connection  = If the Wireless Network Connection icon is not present, this may be due to the wireless network manager of your vendor's card taking over from Windows' built-in one (Wireless Zero Configuration).Please refer to the documentation of your vendor's card in order to turn it off as this may interfere with the procedure here documented.Screenshots are taken from Professional version thus may slightly differ from other versions (e.g.Home Edition, etc.): You have now succesfully configured Windows XP to connect to eduroam network.The Wireless Network Authentication Type Is WPA2 Enterprise If Asked For An Outer Identity , Anonymous Identity Or Roaming Identity , Leave It If You Do Not Choose To Validate The Server Certificate Your Connection Will Not Be Secure.