We must first be careful when you install Linux...

you must install the boot loader (lilo,grub) on the boot partition of the system and not on the MBR.


Then you must create a file that contains the image of the boot sector of the partition Linux:

dd if=/dev/hd1 of=/tmp/linux.sec bs=512 count=1

copy the file "linux.sec" in "c:\" of Windows XP.

You must edit the file "boot.ini" as follows:

[boot loader]
timeout=60
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS

[operating system]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect
c:\linux.sec="Debian GNU/Linux"