Basically you will need a cable, laptop, and the software.

I got an INPA K-DCAN cable off Amazon. I gambled a bit there and just got one of the less expensive ones with good reviews. I had to solder together 2 pins (many cables will need this to work with the E53), but it works.

Laptop, a Windows 7 is recommended IIRC. If not, many have gotten the software to run even on Macs with an emulator.

For software, to code you will need NCS Expert. It commonly comes as a package with INPA diagnostic software, and EDIABAS, which in my layman's understanding NCS and INPA use to connect to your car. You can get them for free online, or you can buy a cable/programs package on ebay.

I use downloaded software that my brother set up for me and I figured out coding from there so I cant give you much info on set up unfortunately.

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04 X5 3.0i auto
03 X5 4.6is