How to capture wireless EAP packets on Windows XP?

I'm testing FreeRADIUS's PEAP-EAP-MSCHAPv2 functionality with a wireless USB adapter (D-Link AirPlus G DWL-G122) on Windows XP (SP2). I tried to capture the EAP packets using Wireshark 0.99.6a but I failed. Anyone can help? Thanks.