URGENT iMovie, GarageBand iPhoto huge problem!!

Let me start by telling you my whole story. First of all, my MacBook has a cracked screen and is plugged into an external monitor. Recently, I tried to install Mac OS X Snow Leopard but that failed numerous times so I gave up and ejected the disc. Then, when I restarted the Mac, I received a question mark icon, so I had to reinstall my original Leopard that came with the Mac. When it was finally done, everything was fine except iChat on the dock had a question mark icon and some of my files were moved to a folder named Recovered Files. I tried to put the files back in their places, but I got a message saying I do not have sufficient privileges and could not find any help for that problem. I tried to open up iMovie, but although it opens normally, it tells me that I am missing QuickTime components, wants me to reinstall and does not play any video, just sound. It is also missing the iLife sound effects. GarageBand does not open and tells me that the instrument library is invalid. It lets me choose an instrument library folder but the message just stays there after I choose it. It also wants me to reinstall. iPhoto also does not open and just "quits unexpectedly" even after I keeps relaunching it. I have tried reinstalling the application bundle DVD, but it hasn't fixed the problem. I also cannot play certain ".mov" files because there is just a black screen with the video's sound or it says I am missing QuickTime components. I also fully updated the Mac to version 10.5.8 and updated everything else.

I am not sure if my Mac is 2006 or 2007, but the specs are: 2.13 GHz Intel Core 2 Duo with 2 GB of ram. It won't let me view anything else and I am missing some things like Disk Utility or System Profiler. I don't know if I explained it too well but please answer ASAP. I have an important iMovie project to finish for tomorrow. Thanks 🙂