In many Dell laptops, there is a setting in the BIOS to enable or disable the bluetooth totally. Be sure that it is enabled. Then check in the BIOS for another setting which lets you turn the bluetooth on or off with a switch or key combinations. We use dell latitudes where I work and usually disable the bluetooth in this way so that when users press the wireless switch, only the wlan card turns on and not the bluetooth.
To get into the BIOS, when the laptop is posting, you need to press the F2 key. Once in the BIOS, you can usually find these settings in the wireless menu on the main screen.