When your system starts [Just after you press power button] keep pressing F8 to invoke hmmm... i dont know lets say a set of menu's will appear in the screen select
"Disable Automatic restart on failure" option now the system wont restart post the error/technical detail line that you see or a screenshot from a camera will help.
A blue screen may be caused due to various reason most likely Memory or HDD or faulty driver or simply to remind you that you are running windows lol
In addition to what hamluis has suggested in the above post you may also want to use a eraser[White soft one] to remove "dust rust" caused by moist/humid climate on your ram chip as it did not work for last 1 year. Be gentle dont put too much pressure you just have to rub from top to bottom of that gold color connector at bottom. Also basic RAM handling ethics is must with static discharge. This has worked for me more than 50 times at least on every old desktops that i came to work on similar problems.