Whenever posting questions on these forums, please give us as much information as possible about your computer. Depending on your issue, we might need the operating system, processor speed, amount of RAM installed, brand name of the computer, (if there is one), and any EXACT error messages you are receiving, plus any other information you think might be helpful. The more information you give us, the better informed our answer will be.
What have you tried to fix the issue? Do you have updated video and audio drivers installed?
In the meantime, please try the steps provided in the links below. It may take a little while but will certainly help the general operations of the computer:
How To Shut Down Unnecessary Start Up Programs
How To Clean Unwanted Files From The Hard Drive
Hope this helps and let us know more.
I've had this problem some time. When I boot up my pc shuts down, but when I boot up again everything loads as normal, I would be grateful if anybody could help.