did this ever work in your possession or is this a dead machine you have acquired and are attempting to fix? did you install some stuff off eBay and now it doesn't boot? did it work before and now it doesn't even though you haven't done anything?
does the board have a modem module installed on it? if so, pry it out. nobody has a way for that to connect anyway.
if no modem module... wait it out, it should eventually time out after a min or so. if it doesn't continue, check the board around the large surface mounted chips for evidence of corrosion or spills. it's WAAY more common than you might think.
try and clean corrosion up with some 99% isopropyl alcohol and a soft bristle brush like a toothbrush) and if it's a sticky goo spill (such as from beer or soda ending up on there) use water and a bit of mild soap (dish soap) and toothbrush, follow it up with isopropyl to rinse and flush out any remnants.
as always allow it to dry thoroughly before trying it again.
if the board is clean and it still wont boot, pull the hard drive connections and boot it up with the start button held down... see if it will go into the test mode without it connected. if it now does, you have a hard drive issue.