To access the Secret Menu:

1. Push down i-Drive knob for approx 8 sec
2. Turn right 3 clicks
3. Turn left 3 clicks
4. Turn right 1 click
5. Turn left 1 click
6. Turn right 1 click
7. Push down i-Drive knob

To get your CIP code (may be slight variations on the below):

1. Go to menu 'Versionkontrolle'
2. Scroll to the very bottom and you should something similiar to "I-05-09-510_050509", where "05-09-510" corresponds to one of the below:

CIP 20.00.00 (Target data Status E060-05-12-500).

CIP 19.02.03 (Target data Status E060-05-09-535).

CIP 19.02.00 (Target data Status E060-05-09-530).

CIP 19.01.00 (Target data Status E060-05-09-530).

CIP 19.00 (Target data Status E060-05-09-510). <- My 2006 525i has this.. Damn time for an upgrade )

CIP 18.00.01 (Target data Status E060-05-06-510).

CIP 18.00 (Target data Status E060-05-06-510).

CIP 17.01 (Target data Status E060-05-06-500).

CIP 17.0 (Target data Status E060-05-03-520).

CIP 16.1 (Target data Status E060-05-03-520).

CIP 16.0 (Target data Status E060-04-09-555).

CIP 15.2 (Target data Status E060-04-09-555).

CIP 15.0 (Target data Status E060-04-09-555).

CIP 13.3 (Target data Status E060-04-09-504).

CIP 13.2 (Target data Status E060-04-09-504).

CIP 12.0 (Target data Status E060-04-06-500).

CIP 11.0 (Target data Status E060-04-03-505).

CIP 10.1 (Target data Status E060-03-12-527).

CIP 10.0 (Target data Status E060-03-12-525).

Source: e60.net (Thanks to mr_london post)