Here's how to get Haiku to work in Parallels:

• Download a nightly build from the Haiku Build Factory [1].
• Rename the "haiku.image" file to "haiku.hdd".
• Use ImageTool to resize the haiku.hdd file to 120MB.
• Create a new VM in Parallels, with Guest OS Type as Windows.
• Set the Hard Drive to the haiku.hdd file that you downloaded.

References

• BeOS related thread on Parallels Support Forum [2]
• Parallels home page [3]