Answer:
Remove the hard drive, turn it on if it still flashes then that's good. If not it's a hard drive failure and considerably more hard to fix I suggest you contact support:http://www.xbox.com/en-GB/support/contact It'll be known as a "Hard disk" probably not a "Hard Drive". However it is likely a hardware failure.
TAKE OUT THE DISC, unplug it completely. leave it for as long as you can, go to work or school or what ever it is you do.
Put it all back in, and hopefully it will work, I also suggest moving it, it could be on a pipe or something which will increase the faults that can occur.
Should the issue STILL occur then there's nothing more I can suggest other than:
http://www.xbox.com/en-GB/support/contact
I hope that helps and really hope your xbox is working again soon.
I live in the UK and can't suggest gamestop and such.
{ 3 comments… read them below or add one }
take i to gamestop or best buy. they wil know what to do with it. they will charge about 15-65 dollars depending on how badly damaged it is. other wise, try messing around with it and press the power buttons a few times.
Number 1 Xbox 360 Repair Guide http://1341dy-7meng7ublc5f4lkeldj.hop.clickbank.net/
I agree you should try gamestop. Sending it in would be rather expensive or you can just get the repair guide which will help. – http://bit.ly/99LEbT