There's a couple of ways to do this.
You can use the win98/winNT install to partition. For 98, you want a minimum of about 2gig, and for NT bump that up to 3gig. That's minimum, so figure your needs from that. Then install 98/NT, leaving the rest of the disk unpartitioned.
Then loadup your Linux distro, and configure at least two more partitions. What I've done is like this:
6.4gig laptop drive.
1.8gig on Windows XP, 2gig to linux "/", 100meg to linux "swap", and 1.6gig to fat32 for games and things I want to be able to swap back and forth.
That fat32 partition is very nice to have if you're trying to get something between the os's. Using Linux to get something from NT isn't tough at all, Linux will read NTFS native. But the other way around can be dangerous.
Then you use Linux's Lilo or Grub to boot with. I use the text version, but there's a graphical version too.
Believe me, the partitioning stuff and loading the OS is about as easy as linux getz.
=)
C@lling it like I c it...