Hi, yes this wireless adapter is compatible with windows 7 (64bit), I am currently running it on my system with zero problems. Other people have complained that this device does not work well with windows 7 due too the driver error. I used the original dlink drivers which seem to work fine, than I decided to switch over to the Atheros official firmware because it was more up to date and those all so work very well. I would recommend the Atheros over the dlink drivers (because of being updated) and if that doesn't work you could always try the suggestion someone else posted below this topic. As for the security mine is currently setup using wpa2 only, using mixed tkip and aes and when in N mode I max out at 270 mbps.
Link to the Atheros driver
http://www.station-drivers.com/page/atheros.htmYou want to choose the bottom right driver under the Reseaux (san fils) current 8.0.0.372
Enjoy!