Unlickly it's not so easy as it should be, since AFAIK loadlin doesn't allow to boot from a iso image.
I never actually tried it, but this should work, however no warranties of course:
1) be sure the iso image has no whitespace in path nor filename (for ex, name it C:\linux.iso)
2) get a GRUB boot floppy (from a friend with *unix) or the dos version from here http://newdos.yginfo.net/grubdos.htm
DONT INSTALL GRUB ON YOUR MBR NOW
3) run grub from floppy or dos prompt and type this commands to grub prompt:
chainloader --force (hd0,0)/linux.iso
4) cross your fingers
5) if it boots, give /dev/hdb as target partition.
As an alternative, you can boot from your distro floppy, then mount your iso image and run the installer from there... what distribution r u going 2 install?