Power windows on the E53 BMW X5 have became known for failing with age, often leaving the window jammed in the fully down position. Earlier BMWs tended to use a 'scissor lift' style window regulator, but around the time of the X5 BMW started moving to a cable & pulley system.
There are actually two separate & common failure points - the cable itself is the first one. It can get jammed or come off it's track, particularly if the car hits a heavy bump in the road with the glass in the full down position. The second is two small plastic clips that attach the glass to the pulleys - the plastic gets very brittle with age but has the full weight of the glass resting on it. When it snaps (and it will) the glass will come off the runner and get stuck. In turn this can then lead to the cable jamming as it tries to pull on stuck glass.
Front Windows
If your window is stuck you first need to find out why - so door card off - it's held on with four torx screws, and the usual plastic clips that can easily break. You can prize the clips with a flat screwdriver, but you may want to pick up a specialized door card removal tool - this will place minimal strain on both the card and the clip. One screw is in plain sight, but one is behind the plastic airbag tag - just pry it out with a flat-head screwdriver. The other two are behind the wood trim. I find the little plastic tools you get for replacing phone LCD screens useful for trim work - angle up the trim at the side furthest from the handle then get a flat-head screwdriver in for more leverage and it should pop out.
The door card is best removed by pulling out towards you at the bottom, then angle up. There will be an electrical connector for the light at the bottom of the card and a speaker connection a little higher. Disconnect both of them. The door handle is connected via a plastic piece that should uncouple quite easily, but the top of the card can be quite tightly clipped to a plastic runner at the very top, so some force may be required to break it free.
With the door card off - can you move the glass by hand? If no, then unfortunately the only real option is to take wire cutters to the cables to free it. There are little access holes for the bolts holding the plastic clips to the glass but you need to raise the window about an inch from bottom to reach them. My experience is you need to remove the glass in order to remove the regulator so go ahead and remove the clips and then the window can slide up to the top. Actually removing the glass from the door requires the exterior trim to be removed around the window. It just pries off but will be on quite tight so be careful not to damage it. With the glass out the regulator assembly just unbolts, then you can put in a new one and re-bolt the glass to it.
Rear Windows
The procedure for the rear windows is mostly the same as front, however there is enough space that you can remove the regulator with the glass held at the top rather than having to remove it from the car. This saves the exterior trim work. A complication is you have to remove the corner window privacy blind (the main blind can stay in place). This is clipped at the top, and can be released with a flat blade screwdriver.
Parts you'll need:
BMW Window Regulator Front Left (E53) - Genuine BMW 51338254911BMW Window Regulator Clip (X5) - Genuine BMW 51338254781
