been without computer for 3 weeks!!

My dimension 8400 finally died after nothing but trouble with it from 6 months after purchase. I bought the expensive warranties. still have a warranty and Dell agreed to replace my system tower with a refurbished tower , which i feel should be new after all the problems I have had and been without a computer for 3 weeks. anyway, they told me I would have a replacement tower within 7 days. It has been 3 weeks!! I call, I write numerous times, no response, no answers, no help. I have had 7 hard drives put in this computer, everything in tower has been replaced 5 times!!! I have been more than patient with Dell. Who can i speak with in corp about this problem? This is totally unfair to me and I am so angry over this. They refuse to call me back!!! Thye refuse to email me back!! What kind of business is this? I have been with Dell since 2003! any help would be apreciated . ty