Followed instructions to a T; however, the new partition it created was an extended partition...I didn't think much of it, my setup was like this, all primary partitions:
begin | windows(45GB) | leopard(25GB) | free space(60GB) | ntfs partition(100GB) | end
Made a new, unformatted partition in vista that occupied the free space, booted to os x, erased it with Journaled HFS+, ran the mergePartition with the 60GB partition as the second argument (was disk0s5) and it somehow erased part of the ntfs partition, leaving 40GB of free space, with the new leopard as 140GB instead of 80GB. Now the setup is this:
begin | windows(45GB) | leopard(140GB) | freespace(40GB) | end
The weird thing is, the 100GB ntfs partition was primary, not extended, so when I made the new partition, why did it have any connection to the ntfs partition? And you can't say that I picked the wrong partition, otherwise I would have 60GB of free space left, or none at all.
I would avoid using vista's disk management to create the new partition from empty space and just use fdisk from the OS X CD if I did this again.