I wanted to backup Leopard using Time Machine and it deleted my NTFS partition and created a HFS+ partition instead. I was wondering if I could reformat it back to NTFS or another partition type later on.
Uh... Macs can't write to NTFS partitions so I highly doubt you ever had an NTFS partition. HFS+ is usually the best format to have you hard drive on. What were you trying to back up?
Leopard will not install on an NTFS partition so you never had Leopard on that drive unless it was reformatted to a HFS+ prior to installation.
So it's HFS+ now. What's the problem?
If you have to use both, FAT32 would work, but I think that using something like a USB flash drive or a network for file transfers would be a far better idea.
You'd have to reformat the drive with disk utility. You'll lose all of the data on the drive doing this.