first add lilo to the MBR of it's drive (/dev/hdb?)
than do a 'dd if=/dev/hdb of=~/bootsect.lnx bs=512 count=1'
this will copy your drives boot sector to your home directory, the file will be called "bootsect.lnx" than get the file onto your windows xp C:\ drive.
edit your windows boot.ini file ( you can use msconfig too I think ) and enter the line "c:\bootsect.lnx="Nonperson iz 50 L337".
Thats all there is to it, basically you put your linux drives boot sector where the windows loader can find it.
Now i've never dual booted from two hard drives before, so I don't know if this will work or not, but you might want to try this instead:
If windows can see your linux drive, and assigns it a drive letter, than you may be in luck. Try and just add the drive letter to your 'boot.ini' file, just a line that says "f:\" or whatever. Windows might be able to do it that way, keep your fingures crossed.........