Beside the USB cable,the NXT have the Bluetooth function.With this, you can make a connection to PC to download your program unto NXT.If you rich enough to buy another NXT, you can connect up to three NXTs to give more abilities to your robots.Besides you can control your robot from PC,you also can use other Bluetooth devices like Handphones, Wiimote etc.
To learn how to use the Bluetooth, just read the Lego Mindstorms User Guide.
Can't connect to the NXT Bluetooth device?Read next how to connect NXT Bluetooth device to the computer.
The problem is
the NXT can only communicate with Widcomm® or Microsoft® stack controllers drivers.My advice is to use some well known Bluetooth Dongle (I'm using Buffalo) , so the probability for BT dongle compatible with Microsoft's driver is high.
First,uninstall the software that was included with Bluetooth dongle
2.Open Device Manager.If you didn't find it.For XP, right click on "My Computer" choose hardware/properties / navigate to device manager.Or you can use the search box at start button.Type Device Manager,and you are done.
Right click on the propietary Bluetooth driver,uninstall all of them.
Make sure your PC have internet connection.Microsoft OS should update it automatically and replace it with compatible Microsoft's Bluetooth Drivers.If not, remove the Bluetooth dongle and slide in again.
When the Microsoft OS done install the Bluetooth driver,you should see "Microsoft Bluetooth Enumerator and "Generic Bluetooth Radio".
Turn on your NXT Bluetooth and make sure it is visible.Refer to the user guide.
Click the Bluetooth icon
Bluetooth Devices window will pop out.Click add and Add Bluetooth Device Wizard will appear.Check the box and click next.It'll find a device.
After the NXT device have been found,click next and tick "Let me choose my own passkey".
Enter your own password.
I've tried to choose "don't use a passkey" before but fail.
Click next and the NXT will ask a passkey.Enter the same passkey you enter before.
Open the BT devices again,click the NXT and click properties.
On the services tab,if uncheck , check ALL the serial port box there.Click ok.
Open the Lego Mindstorms NXT program,click Tools then remote control.On the remote control window click connections.
If still doesn't work.Delete the NXT in Bluetooth Device and click "add" again to create a new one.
Still doesn't work?You can refer to here
1. NXT Step blog
2.Mindstorms support page