Firstly you must mention the proper details in your question for what you want a solution. Secondly, you may ask such questions in the Ask Expert section so as to get better solutions or responses to your questions from the experts. But still if you want answer to your question then I would like to help you.
Computer hanging problems are mainly due to the presence of the harmful viruses on your computer so you can overcome this problem by installing a good antivirus on your computer so as to find the viruses and then remove them. The second reason can be the looseness in the wires attached to your system so you must make sure to check them properly.
The problem which you are facing is related to booting so the solution for that is as under. And if your monitor screen doesn't start up but the fans are working then I have a great solution for it because I have faced this problem just yesterday with my computer and as I know much to overcome such common problems of computer so I corrected it myself. And now I am passing up the solution to you:-
So first make sure that all wires are properly attached to your system. If this didn't work then clean up the dust in your system. If this also didn't work then come to the main one which is the RAM problem so remove the RAM from the slot it is in and then put it up in the other slot and then check it out. If this still doesn't work then ask a friend to give RAM to you then you may try to put it in in the slot of your system. If that works then you need to buy a new RAM to overcome your problem. And if still this doesn't work then come to the solution which I used with my computer which was:- I have a graphic card attached in my CPU's motherboard, I just removed the monitor screen wire from it and then attached the wire to the main motherboard without putting the graphic card in it. And that really worked with my computer. So now I helped you with my response but in future make sure to ask a solution for such problems in the Ask Expert section.
I find that the harder I work, the more luck I seem to have.