PC is extremely slow/laggy after cleaning/dusting the insides and applying thermal paste

LlamaCat

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Dec 23, 2013
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My GPU a temps have been a little high lately, around 101c under load, and I hadn't cleaned the insides in a while so I decided to do that. I got some cotton, q-tips, ethyl alcohol, toilet paper, thermal paste and got to work. I removed my HDD's, my SSD, my GPU, my RAM, CPU fan and another case fan. I took apart the GPU, applied thermal paste, put it back together, applied thermal paste to my CPU, dusted and cleaned the rest and finished up and booted up. However, my PC is now extremely laggy and very slow. I have no idea what's wrong. I'm running Windows 10, and here are my specs:

i5 4670k @ 3.4GHz
MSI GTX770 TF
G.Skill Sniper 2x4GB
Gigabyte Z97-HD3
WD Caviar Blue 1TB
Seagate Barracuda 500GB
Sandisk Ultra II 120GB

Please help, I have no idea what the hell the problem is. Also, here are my temperature readings right now, they're even worse than before:

 
Solution
First off your processor is throttling because it's too hot! Shut it down and remove and re-apply the cpu paste and make sure it is seated correctly.

LlamaCat

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Dec 23, 2013
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I literally just did that an hour ago. Are you sure that's the problem?
 
How did you apply the thermal paste? / Have you ever applied thermal paste before?

The purpose of thermal paste is to fill in microscopic air gaps between the top of the CPU and the heat sink, because both surfaces are not perfectly flat and smooth. The vast majority of the heat transfer is via metal-on-metal contact (and in fact the CPU should run at lower temps than you're getting if you use no thermal paste at all). Thermal paste conducts heat 100x better than air, but it is about 100x worse than metal-on-metal. So it's very important to preserve that metal-on-metal contact.

If you applied a thick layer of paste like a layer of mayonnaise on a sandwich, that's way too much. Use a tiny amount about the size of a rice grain or half a pea size. Apply it to the middle and spread it around by pressing the heatsink down. Squish it around, pushing excess out the sides. I stop when I start to feel the two metal surfaces grinding on each other. Then I strap it down (the compression straps are important because they fold over the tips of microscopic peaks in the metal, increasing metal-on-metal contact surface area). This way you maximize the metal-on-metal contact, while assuring most of the air gaps are filled with thermal paste.

The only cause I can think of for temps that high is that your CPU fan isn't working.
 

LlamaCat

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Dec 23, 2013
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I just removed the heatsinl, cleaned it up and reapplied thermal paste exactly as you said, the size of a rice grain smack in the middle. Reinstalled the heatsink, turned on the PC and it’s still overheating. And yes, my fan is working.