if you are unlucky you might loose some info, but with everything backed up... first defrag the hdd, then shrink the XP partition (there is some tool in Win for it i have heard). you need some 4Gb free.
now you make a 3.5Gb partition and the remaining free (~500Mb if as above) another.
make the 3.5G your / and the 500Mb one your swap.
you should be able to use lilo or XP bootlader (with help of lilo) to load Linux.
you could use NTldr (windows NT4, 2000, XP...) to bot linux (compilcated process but it works).

to do that I let the nt bootloader and lilo work together, quick sketch outlining what i do, write LILO to a floppy, make a "image" of the floppy-mbr put that image on the floppy, boot win copy file to C: \ edit BOOT.INI.
miy BOOT:INI looks like this.

[boot loader]
timeout=2
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOW S
[operating systems]
C:\linux.ipl="LINUX"
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Micro soft Windows XP Home Edition" /fastdetect
a few more details.

1) make lilo write to floppy, have this line in lilo.conf:

boot=/dev/fd0
OR give floppy as an argument to lilo
Code:
lilo -b /dev/fd0



2) make a image of the floppy-mbr and put it on the mounted floppy (mount -t vfat /dev/fd0 /floppy)

dd if=/dev/fd0 of=/floppy/linux.ipl bs=512 count=1

3) Modifiy c:\boot.ini -- add a line with:
Code:
C:\linux.ipl="Linux"

repeat 2) and 3) every time you run LILO.

Microsoft ntldr now believes you have yet another windows installed. happy booting
oh btw, i have several linuxes booting from that same lilo.
hope it helps.[/quote]