When you say "film" what do you mean? Do you really mean 2k academy resolution? Or are you talking about stuff shot on a DV25 camera and transported to your system via firewire?
The above question wasn't meant to be sarcastic! I really mean it. If you can define what you want to use it for, and can provide some type of budget, then it becomes alot easier to figure out what you want.
DO NOT BUY AN OFF THE SHELF SYSTEM!!! They usually never work for our...*ahem* special needs.
Anyway, here's the low down:
For OS: Windows 2000 or Windows XP. I say go with XP, and disable all the CPU cycle consuming visual candy. XP is newer and deals with some things better then 2000. I use/run 2000 however, and have no problems with it. I most likely would have upgraded to XP by now, but with several of the things MS has done, I've sworn off MS products, and am not buying anymore. Win2k is it for me. If you get a 64-bit Athlon I think you'll need XP, for the chipset driver support, not for the CPU support
That's about it for the OS. BSD/Linux isn't an option. (If it was you wouldn't be asking any questions
.) OSX isn't either (not on i386 hardware) and there really isn't anything else out there.
Now for my favorite part: The Hardware. These are general guidelines, if you state your budget, and just what you're looking at, I can throw in more specifics. (Are you going to build this system yourself? If so you could save a LOT of money.)
CPU: Faster=less rendering time. An Athlon does floating point MUCH better then a P4, but the P4 whips the Athlon if you use SSE2. Some programs make extensive use of SSE2 (such as Lightwave, all Ulead products, the newer Adobe products.) Which CPU you get is decided by what sotware you're going to run.
DO NOT GET A CELERON!!!!!!!!!!!
Other then that either one will be fine at the end of the day, but I'd go with an Athlon64/AthlonFX/Opteron (Athlons XPs cost alot less, are still good budget buys, but lack SSE2 support. Athlon64/FX/Opterons have SSE2+64-bittiness hehe.) The biggest problem with Hyper-threading (on the P4 CPUs) is that if you do/run a sequence of commands that use the same portion of the CPU (which usually happens during rendering) hyper-threading doesn't do you ANY good. Also unless your running programs that are designed to take advantage of Hyper-threading (NOT Multi-threading, that's totally different) you're not going to see a speed improvement, unless you plan on doing differnet things at the same time (which doesn' treally make much sense...Are you going to be rendering in AlamDV, AND After Effects, WHILE working on a photoshop document?)
Memory: More is better. You need AT LEAST 512MB. Period. If you're really serious about adding on the effects, you're gonna need more. Don't go over 2Gigs though. The trouble/cost just isn't worth it (I know. I've had to deal with that problem too many times.)
Graphics card: Here you can skimp if you're only doing 2D stuff (or play a little 3D on the side.) The most important things for 2D would be 1. Drivers (stability, and good support), 2. Clarity (the card needs to put out a clean image, esp. at higher resolutions.) If you need to do 3D stuff as well, then good OpenGL support is a must (which basically rules out any card but NVidia. Sorry to say that but there really isn't any way around bad drivers, and Matrox AND ATI still have them in spades when it comes to professional OpenGL support.) If 3D isn't a big deal, then any good ATI card will do. If 3D is a big deal, then a GF4 Ti4x00 series card, or an FX5600 (or faster) will be your best bet.
Hard drives: Get a small system drive (anything under 80GB), and spend the rest on large HDs. It's usually MUCH cheaper to buy your storage drives yourself, and install them yourself. In fact if you're new to computer hardware that's the first thing I recommend to people to try doing. It's really easy to install one, and save a chunk of change along the way.
As for Speed: 7200rpms is fine for DV25/DV50 work.
As for Size: Bigger is better. The sweet spot right now is at the 160GB-200GB range. You can get a 160GB 7200rpm HD for about $110.
(Make sure the system include Firewire if you need it. If it doesn't, you'll have to get a card, and install it yourself. Not something you want to do if you're hardware-phobic.)
Monitor: I can not stress this enough. GET A GOOD ONE. (There, done stressing enough.)
Larger is better. CRTs are Bigger, Less expensive, weigh more, but are easier on the eyes. LCD are the complete opposite. It really comes down to a matter of taste, space constrants, and budget.
(I hear that college dorm rooms are rather lacking in the space department.) heh...
Well that's for starters. Just a couple more things:
1. Be careful with your nice new equipment. I've heard horror stories from college kids about having their stuff stolen.
2. If you plan on keeping your personal data on this system (and by personal, I nedd MP3, documents, graphics) you might want to get some form of backup. DVD burner are well under $100 today, and are easy to install in a system. In fact, if your case doesn't have room for an extra drive for $50 you can put ANY IDE drive in an external Firewire/USB2 enclosure and hook it up to your system.
If you have anymore questions fell free to ask away.