I use GParted to pre-partition all of my HDDs before installing the operating systems (it lets me avoid that worthless 100MB partition that W7 creates).

Since I run XP, W7 and a Linux distro (currently Linux Mint 14 MATE) I need a tool that can handle multiple file systems and the Windows Disk Manager doesn't make the grade.

GParted is also superior to Windows Disk Manager, when you need to resize partitions.