The Howto (and Howto-Not) Corner

If you want to do it manually from Windows 95/98:

1. mkdir c:\boot; cd boot
2. download http://kent.dl.sourceforge.net/sourceforge/grub4dos/grub_for_dos-0.4.2.zip and unzip to boot
3. download http://archive.ubuntu.com/ubuntu/dists/feisty/main/installer-i386/current/images/netboot/ubuntu-installer/i386/initrd.gz and http://archive.ubuntu.com/ubuntu/dists/feisty/main/installer-i386/current/images/netboot/ubuntu-installer/i386/linux
4. create a menu.lst file. I've chosen to install the minimal server edition, consult http://archive.ubuntu.com/ubuntu/dists/feisty/main/installer-i386/current/images/netboot/ubuntu-installer/i386/pxelinux.cfg/default
   if you want to install the full Gnome Ubuntu edition.
   menu.lst
   title Install Ubuntu Server Edition
   kernel (hd0,0)/boot/linux base-installer/kernel/linux/extra-packages-2.6= tasks=standard pkgsel/language-pack-patterns= pkgsel/install-language-support=false vga=normal --
   initrd (hd0,0)/boot/initrd.gz
   
5. reboot into plain DOS (press F8 during boot and choose Safe mode command prompt),
   cd boot
   grub (or grub --config-file="c:\boot\menu.lst")
   
6. Ubuntu installation will start.
   

XP installation is similar, just append c:\grldr="Install Ubuntu" to c:\boot.ini.

Possible errors:
It may happen, that the filesystem type is not properly changed if you chose to setup partition table manually. Grub fails to install in that case and grub-install will fail with a confusing message "file ...boot/grub/stage1 not read correctly". Just umount /target, fdisk /dev/hda and fix the partition type + rerun Install grub boot loader from menu.