The two are both operating systems; having Vista does not mean you can only have Vista on that computer. You can either run them side by side, or remove Vista and install Windows 7 in its place.
Look on the left side of your laptop there should be a switch. You flip the switch and a light should light up on your keyboard telling you that it's on.
Actually,internal-Bluetooth has already been built-in.Just click on start,go to "devices and printers" that located on the right of the start menu(usually under control panel",after that,right click...
Use Dell technical support to download the utility file, then set it up and the Bluetooth hardware is shown. For the Dell website, see the Related Link. And if you need all the correct Dell 1525...