When I installed Windows 10 build 10041 on my 2009 Dell Inspiron 1545 laptop my Bluetooth 365 stopped working. On investigation I saw that Bluetooth had disappeared from Device Manager completely, but no yellow '!' was apparent anywhere. When I checked the BIOS the Bluetooth card was present. I researched the issue for a couple of hours and realised that Dell did not have a Bluetooth 365 driver for anything later than Windows 7. (That Windows 7 driver had worked in Win 8/Win 8.1). I discovered that the card is made by Broadcomm and is also used by Lenovo in some of its laptops. I downloaded the following driver from Lenovo's support site and installed it. When prompted, click the 'update software' button, and a further installation will run. If you wish, have Device Manager open and you will see the drivers and devices install.
support.lenovo.com/.../ds031759
It worked perfectly and my Bluetooth card was detected and configured and now all my Bluetooth devices work with Windows 10.
The Dell 1545 with Bluetooth is a great workhorse PC and it would have been a shame if it could not have been used with Windows 10. I hope it is not a sign of forced obsolescence by Dell, and that they will release Win 10 drivers for this venerable old laptop. It is a shame to have to go to a competitor for a driver. Judging by my web research there are many of this model still in everyday use. I trust this will be of use to other users.