How can fix the issue with BMW's power windows not working?
This is a common problem with BMWs and it is not something to panic about. The most common culprit for a non functioning of power windows in BMWs is a blown fuse. Replacing the blown fuse with a fuse of the same amperage would easily solve the problem. If not the fuse, it would likely be the Window motor. When the windows motor wears out, it could potentially cause the power windows not to work well. Having it replaced also solves the problem. One can't also rule out electrical issues that might have to do with wiring as a major culprit in this. And that would involve re examining the wiring as a remedy.
Quick question though. Alongside the power windows not working, are the locks also working?