99 expedition problem with the anti theft system

I have a 99 ford expedition and about two weeks ago it began to do weird things. At times it beggins to beep for no reason and I have to get in and pull out the little key under the dash so it would stop beeping. Then I've also been having a lot of trouble starting it because when i try to start it , it just beeps and flashes theft on the dash....I don't know what to do and I really need this car....thanx in advance

If you have another key try it the spare key is for your other system to work.
If you have a good spare key try to calibrate another one from this key.
Some locksmiths do key work and the dealer does.
http://www.ntxtools.com/ sells a key calibrator but it costs more than a trip to the dealer.

thanx man...is there any way I could do some type of bypass to make the truck "think" that the chip is always inserted?...because I think that that little part of the alarm system is the one causing all this trouble. Im pretty good with car electronics and have some experience doing alarm stuff....and I really don't have the cash to go get it fixed by a pro...

You could do a google search also check firms like bulldog security they have diagrams and ect. for alarm systems. Look on ebay they sell wiring diagrams for security systems. I purchased an all lines c-d rom for around $19.95 single line were around $8.95. Most alarms have a box and they install an extra key in this box.