What should I download to help me make this video?

I'm trying to make a video, and so far Windows live Movie Maker won't work and neither will Windows Movie Maker 2.6. I'm trying to make a tribute video. So I used a website to download videos from youtube so I could put little clips in my video. Windows live movie maker wouldn't except the files and when I used the other one, I only heard the audio and didn't see anything. I need to be able to add background music with pictures and clips of videos going on. So if the video is 1 minute long, I need only 20 seconds to 43 seconds. I also need it muted because I'll have music playing. I need SOME type of free software that allows me to do this... please help.