The EASIEST thing to do would be to have a computer that you can throw one of the 'easy' Linux distros on and you pretty much would be set-up out of the box; that is, Apache, PHP and MySQL will generally be installed by default (or at least you can request them be installed). I'd recommend Mandriva, Ubuntu/Kbuntu or Mepis for this. Configuration for a basic server set-up is not that hard.
Assuming that you normally run Windows and don't have a spare computer to install Linux on, there are a couple of options.
(1) Get an extra hard drive and install Linux on that. You'll probably have to hand-configure the boot load to boot into Windows but that is not hard at all (and I'd recommend using grub rather than lilo). My main office computer is set up this way; one hard drive for Linux (which it runs 24/7 virtually all the time) and another hard drive with Windows 2000 on it (for those odd times when a client requires me to do something in Winders). Note you can run either as the "main" OS in this setup.
(2) Get one of the "Live" Linux distros (such as Knoppix) and run "live" off the cd. This might be a bit harder to setup, but maybe not, as you'll have to have all your script files ready to go on your WINDOWS disk before you boot off the CD. I use a Knoppix LIve CD for troubleshooting (yes, even Windows systems) in the field.
(3) Set up Windows with "virtual machine" software and install Linux in a virtual machine. Then you can run Linux and all the servers you need there. This would be the "new, cool" way to do it.
(4) Set up all that stuff on Windows. Apache, PHP and MySQL all have Windows ports, BUT you WILL run into some differences. Since your requirements specify a Unix host, I really would try to stick with one of the Linux solutions (1-3 above).
Let me know if you need me to send you a Linux CD or DVD. You can PM me your address and I'll send you one if you don't have broadband to download it yourself. The CD's run about 700 MB each and the DVD's of course are about 3-4 GB. I could easily burn you a copy of Mandriva 2007 on DVD and drop it in the mail. And it's not even piracy.