Computer power button flashing red and not turning on

Help me please. I have just received a second hand computer from a friend and after about a month of having it it has stopped and the power button is just flashing red twice every second. I do not know what model it is as I got it second hand from a business and on it it says reimaged all I can say is that it is a large and very heavy desktop computer and it does not come with any accessories you have to buy a separate mouse and keyboard and plug them into USB ports on the back. This computer has all of my work stuff on it and all of my child's school stuff on it so it would be very helpful if the response could come with some urgency. If you have questions or any think please let me know and I will be more than happy to answer them. Also please call me Chris. Thank you in advance

-Chris