i've never used a floppy disk. cd's can be boot disks too.
so this depends on if you want to install 3 OS's or 4. i'd suggest 3 max with a 20GB hard drive. you may even want to look around on like, ebay for a larger laptop hard drive. i almost have 20GB in music, lol. ANYWAYS, the first thing you need to install is windows. when you go do to that, it'll want you to create a partition for windows but the default is to use the entire hard drive. tell it to use 8GB (or 8x1024 MB, 1024MB = 1GB). once that's installed boot in to windows. PC-BSD is weird and formats all of the remaining hard drive space with the BSD filesystem even if you choose to only use a smaller portion of the hard drive. so what we're going to do, is create another partition for RedHat so that PC-BSD won't use all of the space, but we're going to create it in windows and modify it later.
so in windows, go start > right click on "My Computer", and choose manage. in the window that appears, in the section titled "Storage" click "Disk Management". the right side of this window will now be in 2 sections displaying your hard drive, the top section being textual information and the bottom being more of a graph. in the bottom section, it should say something like (C:) 8GB NTFS | Unpartitioned Space. Right click on the unpartitioned space and choose create partition, make this partition 7GB and if it wants to format the partition, there should be a checkbox or a menu item that has the option to do a quick format. choose that as this will be your fedora partition and we dont really care what M$ has to say about it anyways :] once you've done this there should be 5GB of unpartitioned space left. reboot your computer with the PC-BSD disk in your cd rom drive and boot from that. the installation doesn't take long, maybe 10 minutes? when your in PC-BSD tell it to use 4GB of the free space. it will want to create a swap partition which we'll use the remaining 1GB of free space for. towards the end of the installation (after all of the software has been installed) it'll have the option to install the bootloader, which isn't necessary as next we're going to install Redhat and that will have a bootloader so really itd be pointless to do this but if you're not planning on installing Redhat right away - go for it. it's not going to hurt anything if you do choose to install it. so now that PC-BSD is installed, we want to install Redhat. I've never personally installed redhat, i started with Fedora Core 3 so this installation i'm unfamiliar with, but for the partitioning you're going to want to create a custom partitioning scheme and delete the 2nd windows partition (it should physically be the second one shown) and create a new partition with mount point: / . use the already created swap partition (i'm not sure if you're going to have to tell it to do this or not) but once you've done this continue with the installation and you're good to go. the bootloader should detect your currently installed operating systems.
if you have any problems, post away :]

"In a world without walls and fences, who needs Windows and Gates?"