Newbie: Drive geometry in freebsd 4.10

[Geoffrey Lane]

I'm trying to tri-boot windows, gentoo and freebsd 4.10 cause I don't 
have an extra HD but had an extra slice to install.
the hd is a maxtor 40gb IDE, model# 4d040h2, labeled on it says:  cyl 
16383 / head 16 / sectors 63 / LBA 80043264
when I throw the first install cd in it says the drive geometry is 
(4982/16/63 80035830). I booted into gentoo and used
"hdparm -g /dev/hda" which gave me 65535/16/63 = 80043264
and to be quite honest I've looked but cannot find out where to locate 
the BIOSs geometry but partition magic SEEMS
to indicated physcial geometry of 4982/255/63.
I tried to find information in the handbook about it but couldn't and a 
google for this is overwelming for a newbie
and nothing specifically I can see about my drive geometry...

/dev/ad0s1 -->  WinXP
/dev/ad0s2 -->  Gentoo2004.1
/dev/ad0s3 -->  ** FREEBSD **
/dev/ad0s4 -->  EXTENDED
/dev/ad0s5 -->  FAT32 partition for downloading to on all OSs
/dev/ad0s6 -->  Linux SWAP

I'm not sure which drive geometry I should be using, I've heard of 
issues installing freebsd causes problems with the geometry
and using other os/utils (ghost/partition magic) afterwards. I do not 
want to lose anything on the drive!
If I need the BIOSs geometry, I would appreciate a suggestion of a tool 
to find this out or can I trust the hdparm/partitionmagic?

I would appreciate the help,
Geoff