In this paper, we present new results on the performance of IEEE 802.11n using open system (no security) and WPA2 security for Windows XP and Windows 7. Enabling WPA2 security results in approximately 4.4 Mbps less TCP throughput than open system for both IPv4 and IPv6 on Windows XP and up to 2.8 Mbps less TCP throughput for Windows 7. For both open system and WPA2 security, Windows 7 provides higher IPv4 and IPv6 bandwidth than Windows XP and IPv4 provides higher bandwidth than IPv6.