Yes, you can change your BMW headlights to xenon, but it is not a simple process. The xenon headlights are more expensive than the standard halogen headlights, but they provide a much brighter and whiter light.
If you are thinking of changing your headlights to xenon, you will first need to purchase the xenon headlight kit. This kit contains everything that you will need to change your headlights, including bulbs and ballasts. You can purchase this kit from a number of different places, such as eBay or if you have a BMW dealer nearby they may be able to order it for you.

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The first thing that you will need to do is remove the front bumper cover from your car. This is done by removing the screws that hold it in place. You may then need to remove some additional items such as your headlight washer fluid, and any connections that are attached.

The next step which you must do is disconnect the battery from your BMW. By doing this you will prevent any electrical damage, and will also avoid any accidental starting of the car.

Now it is time to remove the headlight itself. This can be done by removing the two screws that hold it in place. There may also be some additional connectors that need to be disconnected.

Once the headlight is removed, you will see the ballast. The ballast is what sends an electrical current to the xenon bulb. It is very difficult to remove the ballast, so you must be very careful when handling it. You will then need to plug in the new xenon bulb into your old connector, and attach all wiring accordingly. Please note that it may be easier if you have another set of hands when doing this.

Once everything is connected, you can then put the headlight back in place and reattach all screws. You will then need to repeat these same steps for the other headlight.
After you have installed the xenon headlights, it is a good idea to test them out.