There are a few ways. BeOS is an OS but has some versions that are really mostly the same but have minor changes. Those changes affect how one can run it. There are even live CD's that you don't need to have installed. As with all live cd's they run slower as they run from the CD (cd's are much slower than hard drives)
A few things.
One is that the original personal edition was a neat way to try beos. It used a virtual hard drive that was just a file that contained the demo OS. It also had a limit of the ram that a system could have. It needed dos and an older version of NTFS. If you have a fat partition then you can use PE with a special boot floppy that limits ram. We are only talking about the original PE on fat partition.
2- A partition on an x86 box is for most people and OS's the same exact thing. The format of the partition changes how the OS uses that partition. You can partition it just like any other OS. YOu can use Windows ot make or destroy or change the partition. You can not use windows to format it for beos yet. I would not install the BeOS boot manager. It does at least offer a way to save the original MBR unlike all linux distro's I have seen.
Your only problems might be ntfs and the amount of ram. Ram can be fixed and ntfs can't be just yet -again PE version only.
Consider using a live demo that yellowtab has of their Zeta OS. It is a BeOS version with some minor changes. You can't install it.
See bebits dot com for all the beos choices and boot floppies to limit ram. See also bezip dot de for more apps. See betips dot net too for problems.