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.
If, for any reason, the connection turns to Manual, in order to re-connect, just bring up the available Wireless Network Connection window by double-clicking its icon in the tray bar , select eduroam and click on Connect.
I had been able to connect previously, but the connection would always indicate that it was validating.
However, it didnt work, until I disconnected, turned the power off my Wi Fi, unchecked the tab in the authenticate dialog box, clicked ok, then switched the Wi Fi power back on, and reconnected.
I suspect a firmware upgrade probably fixes that behaviour. If you want to accept both computer credentials and user credentials you'll need to name both "Domain Comptuers" and "Domain Users" in your policy.
By default, XP will re-authenticate with the user credential after the user logs-on (there is no way to do computer-only with XP, I believe).