Here are some things you need to consider.
The Dell website has a number of driver updates for your computer. However, you might have some trouble finding a 64-bit driver for the Bluetooth device that is built into your Dell laptop.
And even if you do have the correct driver, your Bluetooth device built into the Dell laptop may be marginal. The fact that other devices you have worked well with your Bluetooth speakers would suggest that.
So here is the quick and low-cost solution to your problem. You purchase a Bluetooth adapter that will work with your operating system and your laptop. These are available from online stores such as Amazon and nNew egg.
A good quality Bluetooth to USB adapter should be under $20 for the generic variety. These often work as good or even better than the built-in devices in your Dell laptop.
The other option the try to diagnose any possible problems with the built-in device, but that would be along and time-consuming process. That is why I think buying the external adapter is the best option at this point.
Bluetooth does not require a lot of bandwidth and if your device is within then a short distance there should not be any connection problems at all. Sometimes Bluetooth receives interference from other devices, such as Wi-Fi routers. But if there's reasonable distance between your laptop and another Wi-Fi device this should not be a problem. In fact, a good Bluetooth device can operate on your laptop while the laptop is doing a Wi-Fi connection. The Bluetooth devices selected channel that is not being used by your Wi-Fi.
By the way, what is the bandwidth of your Wi-Fi device on the Dell laptop? If it is running at the standard 54 Mb per second, it should not cause interference to a nearby Bluetooth device.
If in the event you find your Wi-Fi system is causing interference to your Bluetooth devices, you can change the channel number on your Wi-Fi device and see if that helps any. Some Wi-Fi modes take up quite a bit of bandwidth, in which case you try to move the channel to the upper or else lower part of the low band spectrum. If you use the high band on your wireless device, there should not be any interference with Bluetooth. Bluetooth normally uses the frequencies set aside for the lower band of Wi-Fi and normally has a very narrow channel width as compared to Wi-Fi.
Of course, these are only generalize observations. I still suspect that the problem is with the hardware of your Dell laptop. Just my opinion.
Hope this helps. Please excuse grammatical errors.