My EMachines T5246 Keeps Crashing in the Heat

ya get a compressed air can and blow out fans and heat syncs.  if that doesn't help then you need more airflow. reroute wires in case. add better case fans and ensure holes are sealed as a vacuum so air flows in a path past components and does not become stagnant.  last, try an aftermarket cpu cooler like zalman, this will drastically reduce your core operating temperature

should not be too difficult; here some steps :
open PC, and clean it from dust  - as said above;
check also video card fan !
monitor your temsp with speedfan, so you know where the problem lies (cpu, disk, video)
http://www.almico.com/speedfan.php      
if the cpu is overtemp, you may need to replace the heat paste, or fan
if you do this, check that you mount the cpu heatsink flush against the cpu !!

here a youtube :  http://www.youtube.com/watch?v=4OB1hxxKdec
info :  http://en.wikipedia.org/wiki/Thermal_grease

with the case open, have a big fan blowing into helps als !

go to BIOS setting and ensure that the FAN of CPU is on Auto mode or increase it .

clean it from dust by blower

add more fans to the cpu ... it will help alot

Thank-you for the thorough answer.

Thank you amigan_99

i thought i deserved a bit here...:-((