I know I had help with this not too long ago, but it still isnt perfect. I still get the edges and unwanted lines around my special effect. I have done everything right as I was told. Is there something else I have to do besides using the Chroma Keyer? I have downloaded demos to particle illusion and fx studio, but they are really hard. Is there a program where I can just add a video clip, and place the special effect on. Vegas is the closest I have come to this, but as I said there are still lines and edges, especially when using special effects that come with white backgrounds.

Sorry for needing help all the time. I really want to add some effects to my movie for my end of the term college project

Chroma Key is not perfect! Never will be...you can spot it a mile off, whether its on Hollywood Movies (Traveling matte),UK Blue Screen or American (and BeeB), Green Screen ........best left for TV Newsrooms. In all these formats its instantly discernable to the half trained eye. Its only a toy. You want an explosion? Then get your camera out and film it for real. Have a look at the other plug-ins though....some really good ones.

I think that TWIY means that Sony Vegas'es Chromakeyer in particular is cheap and problematic.
And he is right.
While it is true that Chromakeying is a very tricky process to get good results out of, the Chromakey filters in After Effects produce much better results with less effort than the filter in Vegas.
It always gives the Halo.