Guys, I really need some help with this if you could.

Over the last six years that I have been brickfilming, I had been using a very old and slow computer to edit with Premier Elements 1.  The was a horrible experience, as my computer could barely take it, but somehow, through several crashings, I always managed to at least come through.

Earlier this year, my mum got me a new computer for editing so I wouldn't have to go through so much bother with a nine year old one.  I got into Premier Elements 9 and started editing Leprechauns in France, but I it's really, really laggy.  In fact, it is even slower than my previous computer ever was.  Selecting a group of files takes an entire minute because of lag on the box selectors thing, and moving a single thing makes the program have to stop and load for several seconds.  And then once I put enough work into it, the program crashes, and it cannot load my save file any more at all.  Each attempt crashes the program.

I've tried restarting the editing process around about five times, each with the same result.  My mum even tried maximizing the amount of data the program could process and minimizing the size of the files I'm using, but it still does not work.

My question is what is the problem and how do I fix it?  My computer is new, and it's behaving worse then the one I have had for nine years, but only in the respect.  In any other situation my old computer can barely do anything.

I need to finish Leprechauns in France by Saint Patrick's Day, and if this problem does persist, I will have to move all of the files to my old computer and finish on that.  It will be miserable, but at least the project will actually go somewhere.