Disk Geometry

[ras bsd]

Hello list, this is my first post here.

My problem is:

I've installed the OS in my laptop in this order, Win XP and Debian
GNU/Linux. I'm trying to dive into the freebsd world from many years
in GNU/Linux. When i start the installation, when i have to enter in
the disk partition section an error appears saying that the disk
geometry is not valid and, anyway, I can not see the free disk space
that i left free after the other OS. My scope is keep working the
three OS.
How can i know the correct disk geometry? What am i doing wrong?

Mi laptop is Intel Core2 Duo and the Hard Disk is SATA 200 Gb Toshiba
MK2035GSS-(S1).

Thank you.