For this example, I’m dividing a 20GB IDE hard drive between Windows XP and OpenBSD. The first 7GB of the hard drive hold a standard install of Windows XP, on a FAT32 file system. I want to put an 8GB OpenBSD install immediately after that. Prepare your hardware as you normally would, and boot off your OpenBSD installation disk. The install process is identical up until the point you see the disk usage menu.
Available disks are: sd0 sd1 wd0. Which one is the root disk? (or done) [done] wd0 Do you want to use *all* of wd0 for OpenBSD? [no]
We don’t want to use the whole hard drive for OpenBSD, so take the default. This brings up a whole new tool, OpenBSD’s interactive fdisk(8).