Question : Problem: THE COMPUTER SHUTS DOWN (JUST LIKE PULLING THE POWER PLUG OUT) AFTER 3-5 MINS.

THE COMPUTER SHUTS DOWN (INSTANT POWER OFF) AFTER 3-5 MINUTES.
BOTH THE PROCESSOR AND THE CASE FAN SPIN BUT NOT AT START UP, ONLY FOR A VERY SHORT WHILE AFTER RUNNING, THEN THEY STOP. I USED A DESKTOP FAN TO COOL THE COMPUTER AND THIS WORKED AND THE TWO INTERNAL FANS WORKED MORE OFTEN. BOTH INTERNAL FANS WERE TESTED BY BATTERY AND WORKED FINE BUT I HAVE CHANGED THE PROCESSOR FAN FOR A NEW ONE ANYWAY WITH THE SAME RESULTS.

THANK YOU

Answer : Problem: THE COMPUTER SHUTS DOWN (JUST LIKE PULLING THE POWER PLUG OUT) AFTER 3-5 MINS.

Fan speeds are set by modifying the amount of time power is applied to the fan digitally. If the power that is getting to the fan is too weak, it would not supply enough power to move the fan. It's possible that the airflow from the fan you were blowing on the machine provided enough assistance for the blades to turn. Otherwise it's very counter-intuituve that cooling off the PC would make the fans work harder.

My suggestions are to swap the power supply for a known good, it's possible one of your rails is getting weak. Also I would inspect the motherboard for bulging capacitors. If you're not familiar with this problem, here is more info:

http://www.badcaps.net/pages.php?vid=5

If you find that you are affected by bad capacitors, you must replace the motherboard or do some real intricate solder work to replace the dead caps. Good luck!