Hi Mouad
We no longer provide LPC2468 header file for LPCXPresso IDE. This part is already end of life and not recommended for new design. If you must choose it, please check Keil MDK. For more information, please see:
https://community.nxp.com/t5/LPC-Microcontrollers/Lpc2468-header-files/m-p/1900175/highlight/false#
Have a nice day,
Jun Zhang