If you run a BeOS-only machine, you rock. But how do you install BeOS Personal Edition if you can’t boot into Windows and you don’t have a Linux installation? Simple. And you won’t have to worry about the 500MB partition size limitation, either.
First, download and decompress the BeOS4Linux package from one of the mirrors. It contains just the raw disk image and a floppy image. Create a new directory in your root, something like /BeOSR5. Mount the image in the new directory, like this:

mkdir /BeOSR5
mount ~/home/Downloads/image.be /BeOSR5

Now just use the Installer app (in the Applications group in the Be menu). Choose the just-mounted volume as the From: volume and your existing BeOS installation (or a fresh partition) as the target. Let ‚er rip and 10 minutes later you’ll have BeOS 5 installed on that partition.
If the mounted partition does not appear to Installer as a From: volume, use this technique instead:

copyattr -r -d /BeOSR5/* /boot

where /boot can be replaced by any volume name you want to install to or upgrade.
Re-run bootman if necessary so you can boot into the new OS from the boot menu, and you’re golden.