I had a nifty reply about trying Adobe Premiere Elements* for your PC since it seems pretty popular.... but I took a closer look at Adobe's site and it looks like a bit of a handholder to me. So I won't suggest getting it.
I use a Mac for video editing because I have always had Macs. I started with iMovie and now use FCP, but software alone doesn't make your movies work. There was even a zombie movie made in my city that got cinema release (and good reviews. well, OK reviews. it was a zombie movie after all...) and it was all cut on a PC using Premiere and After Effects. I read an interview with the creators who complained the PC was crashing every half hour by the end of the project, but dammit they got it out the door. That's movie making.
Feel free to buy a Mac, I love my 24" iMacs (home with FCE, work with FCP) and learning FCP may get you into the industry if that's where you want to go, but if you just want to noodle around a bit with editing, grab something decent for your PC and see how you go. The fundamentals are the same, even if the keyboard shortcuts are different.
IMO, a Mac Pro is overkill for FCE/FCP. You might get some value of of all those CPU cores, but it's an expensive machine. Even a 21.5" iMac is a beast these days - better specs than my not-quite-top-of-the-range iMac I bought a year ago for a grand more. (make sure you get the full size wired keyboard)
The first time I saw video editing done on a Mac (on a Quadra, IIRC) I said: "That is so cool. One day, I am going to do that." And now I do. My only regret is that I meandered into it. If you want to really do video editing, grab it with both hands and do it.
(*assuming your PC is up to spec for it)