Let by honest I do not know much about Pcbsd .
So I like to try it
What is my problem ?
Well I have 3 HD the BIOS allow me to boot from all the 3 Drives
On sda I have windows and opensuse 11.1 as a dual Boot
On Sdb I have Fedora 8,9,10 as a triple boot
On Sdc I have Mandrive alone at this moment
On SDC I have a free 70 GB
What I like to do is to install PCbsd 7,1 on that free space and install
the boot loader on sdc.
Pcbsd recognize my hds and free space it gives the option to install boot loader or not install.
As I like to do a dual boot Mandriva and PCBSD I have to install
a boot loader.
But up to this point it DID NOT given my the option where to install
the boot loader.
Maybe I am too cautious , but I have try PCBSD 6 and was a total failure
I do not like to messed the rest of my OS
BTW I have download 2 install CDs

To prevent the MBR on sda getting overwritten, a convenient
solution would be to change sda to a dummy one, if you have
a spare harddisk. ( BSD writes to both MBR and superblock,
so it's no problem booting it from anywhere.)

'sdb' could be replaced with a dummy too, during install,
... the BSD drive id's are cryptic, just to be absolutely
sure, nothing gets installed on the wrong disk.
( May be the pcbsd installer is more friendly, I have it
installed, but don't remember, how it worked.)

Else: Start booting into Suse and setup grub to superblock:
# grub, grub > find /boot/grub/stage1, grub > root (hd0,3),
grub > setup (hd0,3) ...... replace '0,3' with actual Suse
partition.

So now Suse is easy to boot with e.g. 'Smart Boot Manager',
if the MBR gets overwritten.

BSD can only be installed into a primary partition.
Suggest : Use 'gparted' livecd to make another primary
partition.
( Gparted can make 4 x primary, the Mandriva tool
'diskdrake' only 2, the second = extended ? )

"Smart Boot Manager" http://linux.simple.be/tools/sbm
( will boot BSD, Linux, win, cd, floppy ... )
....

P.S.: You will need both install cd's, PCBSD.

Good luck !