Laptop HD change

[Villamad]

I have a ibm thinkpad T20 and am looking to change it's harddrive, it is running windows 2000 which i hate, i have a 20gb hardrive lying around which is bigger than the one in the ibm, by 6gb plus it's also runnig xp pro which i reall y enjoy using is there anyway i can just swap these or are they completely uncompatiable

[Villamad]

Please any1