The The Intel WiFi Link 5000 family
adapters have Dual-Band, Quad-Mode functionality, which means they support 802.11a/b/g and Draft-N in both the 2.4GHz and 5GHz bands.
In fact to get those higher levels of performance you need to use the 5GHz band, which supports channel bonding
, where two channels are used simultaneously for higher bandwidth. Channel bonding is only supported in the 5GHz band on Intel (and most other) adapters because there are only 3 non-overlapping channels in the 2.4GHz band. This is sometimes called "Friendly Neighbor Assurance" since it prevents one from essentially taking over most of the 2.4GHz band.
BTW, I'd recommend the WiFi Link 5300, which has a 3x3:3 (transmit antennas x recieve antennas : spatial streams) configuration supporting up to 450Mbps, vs. the WiFi Link 5100, which has a 1x2:2 configuration supporting up to 300Mbps. Of course if the access point doesn't support 3x3:2 as well, then that won't really matter. <g> Scott.