Basically, any install of grub will do about the same as XOSL but you do not need an extra bootlader partition.
Harry gave you a very good advise which is to always install the new bootloader
in the partition boot sectors and NOT modify the mbr of the disk.
Then you can add the a new entry in the grub config file menu.lst
located in the partition of the grub which is called first at boot by the mbr.
Grub has a very nice feature which allow you to edit ("e" key), temporarely and
on the fly the menu.lst or just go into a console command prompt mode ("c" key).
From there you can try out various configurations and do not need to complete a boot
to only update the config file. From the command prompt, the "tab" key will do autocompletion
for both the path and the commands you can execute. You may have a check to the help or man pages.
The following menu.lst entry will allow you to boot from a partition bootlader
(your new linux install) which could be an other version of grub, lilo, or ...

title name_of_your_new_linux_install
rootnoverify (hd0,6)
chainloader +1
boot

hd0 means first disk recognized by the bios, 6 is hda7 and so on. Remember to use the tab key for autocompletion !
Grub will even tell you the partition type, and the tab key at the prompt will list you all the possible commands.
Grub has a lot of VERY powerfull commands and tools such as boot from floppy & hdd images,
alternate boots, time out, password, network boot (pxe), swap hdd, change active partition, ...
I personally like to use grldr which a port of grub to be used and started from the xp bootloader
using a boot.ini entry, and the dos port of grub, grub.exe to boot from my USB dongle keys, cf:
http://www.knoppix.net/forum/viewtop...?p=93758#93758
Hope this helps,
Gilles