Lisa,
Talk about jumping straight into the Shark Tank without a knife, snorkle, floatation device or knowing how to swim! I hate to say it, but starting from zero and with no computer on hand to do this stuff... wait. Have you ever used a mac? If you haven't, there's another learning curve issue you don't want to deal with when under the gun on a deadline.
Okay, at the moment your best option is Movie Maker. Yeah, you can't do all the 'whizbang' stuff like with dedicated Non-Linear Editing Software, but right now all you need is to be able to make basic cuts (stay away from those funky transitions. I repeat stay away from the transisitons!)
Runaway is correct about backing up your clips and your editing files. You'll need a USB (Firewire capable is better) External drive with a capacity of 60GB or better and a USB stick drive of 2GB or better. The external will hold your video files and your stick will hold your project files. You want them separate so you can save your project on both drives as a back up if anything happens to your external.
Next you need to know what type of video your team is shooting. Standard DV or High Definition. If it's DV, no prob. If it's HD, prob. WMM up to Vista does not do HD. It doesn't come with Win7 Pro (which is most likely what your school has if it doesn't have Vista Pro) so it will have to be downloaded from MS (which your school's IT dept. probably isn't going to allow.) You definitely must find out what video format they are shooting in. If they don't know, look up their camera model to find out what formats it shoots in. My suggestion is if principal photography hasn't started yet tell your team to shoot in DV! If they get the 'we wanna shoot in HD for the quality' horsehockey, ask them how they're going to get it edited. Without a computer with the capacity and software to edit HD video you're dead in the water.
Lastly, scour the video tutorials on both shooting and editing. Pay particular attention to; screen direction, continuity and cutting on action. Don't forget to take plenty of notes! Oh and if you're going to roll with Movie Maker, get "Microsoft Windows Movie Maker 2" by Jan Ozer. You can order a copy from Amazon pretty cheap. Good luck. You're gonna' need it!