dropped laptop - messed up display

Hi - I hope someone can give me some advice on my problem (well, nobody can help my clutzyness, but maybe someone can tell me what I did to my laptop).

I have an XPS M140 running Windows XP that I bought just over 3 years ago, and I found some info on the Dell site about the computer I bought.  It said I had a liquid crystal display 14.1 WXGA. 

I frequently use my laptop while sitting on my couch, and two days ago it slipped off my lap and dropped about 1 1/2 feet to the hardwood floor.  It was on when it fell, and it landed upside down, slamming the top closed.  When I opened it back up, the computer seemed to be functioning normally, and nothing was visibly wrong, but after a few hours the screen went dim.  The next day it would change back & forth between dim & normal every few hours.  Today it is only dim, and there are horizontal lines that correspond to images on the screen.  For example, the horizontal grey borders of the text box I'm typing in has lighter areas extending out from it to the edges of the screen.  These bands move with the image when I scroll.

I tried running a troubleshooter from the Dell site, and it had me download a driver (something to do with BIOS??), but when the computer restarted I got the following message:

"An unexpected error occurred while running the Flash application.  Reboot and try again.

Application error return: 0x00000604

Windows error return: 0x00000002"

If this helps with diagnosis at all, I've done something I know I'm not supposed to do, but it has an effect on the screen: if I torque the screen (push the uppper right edge and pull the upper left edge) the screen returns to normal, but only as long as the screen is held in that position.

Any ideas what I have done and what I have to do to correct it?  I've heard people say that if you mess up a laptop screen that you might as well just buy a new one, and I'm hoping that isn't the case as finances are extremely tight right now.

Any replies will be appreciated.  Please assume I know very little about computers, so simplistic / basic language and/or step-by-step info would be most useful & helpful to me.

Thanks!