high cpu temp.

A while ago, my pc started acting weird while playing games.. I currently play League of Legends, Mass effect 2-3, and used to play Star Wars online (but stopped during these probs). Firstly when i played a while, my graphics card would crash ( gigabyte ATI 5850 1gb) and weird vertical random colour lines would show up in my screen, so it needed Restart. I assumed normally its my gpu, checked the temps and they were too high.. I started playing by manually adjusting the fan speed in order for my card not to crash. This worked for a while, although after some time the pc just Shut down .. No graphic crash.. just shut down.. I decided to to change my graphics card to an old one i had , GTS250 nvidia 1 gb ddr3. Now there are no graphic crashes but the computer keeps shutting down when i play e.g mass effect 2. I check the temps and now Cpu temp is above 89c when i start the game.. even though its stable temp is 51c to 50c. What is wrong..? I dont know seriously.. Ive cleaned the case several times ( to the point i can) but nothing seems to work.
Complete System specs : CPU Type QuadCore AMD Phenom II X4 Black Edition 965, 3415 MHz (17 x 201), Ati5850 ( gts250 now), Motherboard Name Gigabyte GA-MA770-UD3 v2.0 (2 PCI, 4 PCI-E x1, 1 PCI-E x16, 4 DDR2 DIMM, Audio, Gigabit LAN, IEEE-1394) 6gb ram Transcend ddr2 (2gb x3). Power supply : 550w chieftec. Please help me.. im desperate..

 

Try refreshing the thermal paste between the heat sink and the CPU.
Clean ALL the old off first and don't apply too much.
A dab the size of a match head is about right.
Apply in the center and spread evenly with a razor blade or stiff card.
Too much is as bad as not enough.

 

I would agree with hrlow its sounds like the tim hasn't been apllied properly,here are a few things to try as well.

Take the side off your case and leave it off do your temperatures go down?, make sure your cpu fan is spinning,feel the side of your cpu heatsink is it warm or hot? If not you need to reapply thermal past as Hrlow said,that is of course if your cpu fan is spinning.

Use this program to monitor your temperatures then take the side off your case,post your idle temperature.

http://majorgeeks.com/SpeedFan_d337.html

While monitoring your temps run this program and your cpu fan run this program,select just stress testing and let it run,your cpu fan should start spinning faster so listen for it,run it for about 10mins until it reaches maximum temperature or crashes.

http://majorgeeks.com/Prime95_d4363.html

Post the results and welcome to the forum