Well, that can be a touchy question, and I don’t want to start a Mac vs. PC flame war here.
It is my personal belief that the less you know about computers, the more a Mac system makes sense. There are a lot more software/hardware options and support out there for the PC, but you will run into compatibility problems more often than with a Mac system, and unless you know how to fix them you can run into some major headaches.
Despite not having as many options, there are still some excellent programs out there for the Mac that will allow you to do just about any movie making related thing you can imagine.
Get whichever system you’re more comfortable with. Just about any G5 equipped Mac or Pentium 4 equipped PC has enough horsepower for DV editing and audio work. Get at least 512 MB of RAM and a second hard drive of 100 Gigs or more to dedicate to video data, and you’ll be in good shape. Firewire ports (to connect your DV camcorder to your computer) are pretty standard these days, but you should double check that your system has one.