Inspiron 1521 will not start up

Hello everyone, I am so hoping someone will be able to help me. I have had an Inspiron 1521 with Vista for 3 years now and it's finally dying, so I got a new laptop and I want to transfer all the files from the Inspiron to the new laptop (not a Dell). However, the Inspiron now will not start up at all. I press the power button on the hinge cover and the power and bluetooth blue lights go on on the right hand side of the keyboard, but the power button itself does not light up. I can hear some things going when I press the power button, as if it's going to start up (maybe it's the fans I'm hearing?) but then it just stays as a black screen. It doesn't go to the Dell logo page or start up windows, it's just black, not even with any back light to it. I've tried starting up with just the battery, with just the AC, with both; I've tried taking out the battery and the AC and then holding the power button down for 60+ seconds and then reattaching the battery and/or AC; I've tried removing the hard drive and DIMM A and B; I've tried just using compressed air to clean it out. Whatever I do the computer will not start up. My AC adaptor is working (it's plugged in and the green light is on) and my battery is probably only a year or a year and half old. This happened once before, probably about 2 weeks ago, and I just shut the computer down and let it cool off and then after a few hours I tried again and it started up fine. Today, though, I've left it for hours right side up and upside down trying to let it cool off and take a rest but it still won't turn on. I only need this thing to turn on once more so that I can transfer the files so if anyone has any tips please let me know! Thanks so much in advance.