I just got the T2450 from ebay, and installed it, and it works!!
Thanks for the info, and for all the other folks that wondered, I can confirm this will work!
I have a Fujitsu Siemens Li1720 with a celeron 1,46MHz 533 bus 1MB cache
and I want to upgrade the cpu, looking at some pentium M's and a core 2 duo
do I need to upgrade the bios or something, or is it just to swap?