mcavic - 4:24 pm on Feb 21, 2008 (gmt 0)
install windows first, make sure your unix install has the ability to set up dual boot, then install the unix second
That's the easiest way. If Unix is already installed, you should still be able to do it, but maybe not easily. In that case, install Windows, then boot a Unix rescue CD. From there, you'll need to edit the bootloader configuration to point to the Windows partition.