either the LCD or the cable that connects it to the video card.   I assume the computer is no longer under warranty?  If it is under warranty, call dell and have them repair it.

 

If not, let me ask one more question.  Is the screen always messed up from the moment you turn it on (does the Dell screen that appears when you first turn the computer on look normal)?  If the Dell screen looks normal it may yet be a software problem.  If it looks bad as well, it's time to investigate further.

 

I am not overly familiar with LCDs and your notebook is one of the few that does not have an online service guide.  The only thing I can suggest is to reseat the cable leading from the motherboard (video chip) on your computer to the LCD.  On most dell laptops this can be accomplished by first removing the keyboard and then something removing a metal cover under the keyboard known as an EMI shield.  Most notebooks are somewhat similar in how they come apart.

 

Here's a link for removing the keyboard of an inspiron 1100:  http://support.dell.com/support/edocs/systems/ins5100/en/sm/keyboard.htm#1105383

 

And here's the link for removing the EMI shield under that (basically just removing a single screw):  http://support.dell.com/support/edocs/systems/ins5100/en/sm/palmrest.htm#1084976

 

Again, I've never seen the inside of an i1000.  You're looking for a cable running from the main board of the computer to the LCD.   On the i1100, you can see this cable in the top left of the card in this picture:  http://support.dell.com/support/edocs/systems/ins5100/en/sm/palmrest.htm#1105456 .  It's the one that looks taped down to another piece of metal.  It will likely look different in your case and will likely be attached directly to the board and not to a seperate card sitting in the board as with this picture.

 

When you find this cable, unhook it and then reconnect it.  Test this.  If this fails you can also try reseating the other end of the cable (where it attaches to the LCD) though this one is much more of a pain to get to.  You can see an example of what you will likely need to do here:

 

http://support.dell.com/support/edocs/systems/ins5100/en/sm/display.htm#1084976

 

If this solution fails then there is likely a problem with the LCD itself -- I'm not familiar enough with such problems to suggest possible solutions, if there are any.