I've set two SSIDs and told them not to synch. Now connected at both 2.4 and 5.
I plugged my Netgear dual band dongle into the old laptop and have two connections - the laptop card at 2.4 and the dongle at 5, with two SSIDs. That's either very interesting, or I need to get out more!
Dell Studio1558 with Win7 Home Premium
HP Pavilion netbook Win8 8GB RAM
IE11 and Live Mail
BT Infinity 2 via HH5
(Virgin 150Mbs as backup)