Try to install Windows NT first. If you want to use NTFS for your Windows NT-partition, keep in mind, that the todays production version of Linux cannot access NTFS partitions. An alpha driver that can read NTFS-Partitions is available at http://www.informatik.hu-berlin.de/~loewis/ntfs. You may create a separate FAT-Partition for data exchange or you have to use DOS-formatted floppies.
Another Mini-howto recommends not to use NTs "Disk Administartor" to create the Linux swap- and root-partitions. It is sufficient to see the free space there. I also recommend to use linux's fdisk later.
Now boot linux from diskettes, create the swap and root-partition. Fdisk assumes the ntfs-partition to be a HPFS-partition. This is normal. Boot again from diskettes and install Linux as you like.
Just in case the installation procedure suggests that you could mount the HPFS partition which it has found: Ignore it.
When you come to the Lilo-Section, specify your Linux-root-partition as your boot device because the Master Boot Record (MBR) of your harddisk is owned by Windows NT. This means that the root-entry and the boot-entry in your /etc/lilo.conf have the same value. If you have a IDE-harddisk and your Linux-partition is the second partition, your boot-entry in /etc/lilo.conf looks like:
boot=/dev/hda2
If you have two disks and your Linux resides on the first partition of your second disk, your boot-entry in /etc/lilo.conf looks like:
boot=/dev/hdb1
Run lilo with a kernel that matches your system. Check the kernel by booting from diskette first if you are not sure.
If you cannot boot Windows NT now, you have a problem. I hope you have created a repair-disk recently.