Hi,
If you install the Cisco Aironet Client Utility (ACU) which you can download from Cisco it will install the Cisco Protocol (IEEE 802.1X) drivers into XP.
I found it better testing EAP-TLS with the Cisco client (ACU) first as it gives you a whole lot more information such as connection info, and stats than using the Windows driver, one you have it working then you can switch to "use Windows to configure my wireless network settings"
Rgds
Paddy