[CentOS] Why so many updates already for CentOS 5

Fri Apr 13 10:17:58 UTC 2007
Mário Gamito <mgamito at telbit.pt>


I've just installed CentOS 5.
I issued a yum update, and to my astonishment there are already 75 MB of 
And i didn't even installed X.

Why is this ?

Warm Regards
:wq! Mário Gamito