Well, there are some tips I can give you. There are much better video makers, but I think they'll agree with me in these things.
First of all, you need the idea. You have to know what you want to do, what message or idea you want to transmit, or what's the story you want to tell. Then you'll have to chose the song. Usually one has the song and the idea that goes along with it and it is then when one thinks "and now?".
OK, so if you have those things, you need the software. This is easy. If you have Windows (any version) there is this program called "Windows Movie Maker". It'll do. No really fancy things like two superimposed images or the chance to put music and sound, but for the beginners it works. If you really, really, wants something with more options I'd recommend "Sony Vegas Movie Studio" (but you have to pay for it or... errr... download it and don't pay for it

) The "Windows Movie Maker" works fine, especially if it's your first video, it makes you realize things and all.
OK, about the videos. I don't know if you have "Enterprise" in AVI or in DVD. If you have them in AVI, no problem, the video program can automatically read them (although in Windows Video Maker it takes some time). If you have them in DVD, you have to pass them to AVI. There are programs that can do that, like "DVD ripper" by Xilisoft or "DVD2AVI" (which is very rough and simple, but it's free and it really works for me). Again, have a good idea of what you want, because this way you could take the parts that really interest you and you will gain time.
About the requirements. I have a Pentium 4 with 512 of RAM and I can do videos, so I don't know if it helps you (I could make them even with 256 of RAM, but it took more time).
The time you will require for each video depends on your skills, your idea, the amount of shots or scenes you want to use, the timing you are going to use... I don't know, ¿from 6 hours to 3 days? It depends a lot on you. If your video have big and long not cut scenes it would be easier, and the beginners usually do that (I know, I was one of them, I still am in some ways

), but I usually try to match images and song and try to offer different scenes, even if they are very short, for every line in the lyrics and such. When your song has some kind of percussion part, trying to match each beat with a new image is cool, but I warn you, it's a pain in the ass to get it.
So, I don't know, that's what I can tell you. If you want any specific piece of advice or something, please, tell me. I'll gladly help if I can.