Computer starts, but nothing happens. Is it the processor?

[ExasperatedVulture]

I tried searching for similar topics. I went through several pages, but I couldn't seem to find one that matched my situation.

Anyway, I started my computer one morning and nothing came on the screen.

There are two lights on the top of my computer. A blue light with either a sun or gear symbol under it. And a green light with a cylinder symbol under it. When the computer starts, the blue light always comes on, and the fan on the top and back side of the computer start. If the green light comes on, the lights on the keyboard and mouse come on and as far as I know, the computer starts like normal. I'm not sure if the green light stays on the entire time the computer runs or if it's just on while the computer starts up. I know that the blue light stays on for the entire time that the computer is on.

So, I started my computer that morning and nothing came on screen. The blue light came on, and the fans started. the green light didn't start, and the keyboard and mouse didn't light up like they normally do, and nothing came on the screen. I sent it to a friend, who works some manner of IT job and says he's built several computers. He ended up saying the problem was the motherboard. I bought a new motherboard and put it in the computer, then hooked everything up. I don't know much about computers, so I just took a picture of where everything was plugged in and plugged it into the same place on the new motherboard (I tried to buy similar motherboards). I started my computer, the blue light and the fans came on, then the green light came on, the keyboard and mouse lit up, and the normal start up screen appeared. The computer was seemingly fixed.

About two weeks later, the computer was back to not booting again. The same situation; blue light on, green light off, no signal to keyboard and mouse, nothing coming up on screen. Also, there wasn't any beep code either time. Another friend of mine checked out the computer. He guessed that the problem this time was the processor. His reasons for this were:

1: The computer starts, and the computer seems to get power, so maybe it isn't the power supply.
2: The motherboard is brand new, and the green light on it also comes on, and the fans attached to it get power, so maybe it isn't the motherboard.
3: Everything is properly connected.
4: He said something about it not being the video card, I can't remember why. It involved plugging something into something else, and afterwards still not getting anything on screen. So for that poorly remembered reason, maybe it isn't the video card.
5: The RAM sticks are properly connected, so maybe it isn't the RAM.
6. When I put in the new motherboard, I had to remove the processor and attached fan. When I put it back in, I didn't put any thermal paste on the processor. I'd never heard of thermal paste at the time, and didn't know it was a thing. I noticed that the processor had some sort of glue residue on it, and just assumed someone had glued the processor to the metal thing attached to the fan thing for reasons beyond my understanding. I didn't know I needed to re-apply thermal paste (which I didn't have). The residue on the processor was only on a fraction of it.

I've since read a bit about how to apply thermal paste. From what I've read, the processor is supposed to be entirely covered in a very thin layer of thermal paste. I've read both one millimeter thin, and paper thin. The purpose is apparently not to keep the heat sink (I'm assuming that's the copper colored metal thing attached to the fan) from touching the processor. That's what I'd figured it would be. Apparently the purpose is actually to fill in the tiny gaps between the surface of the heat sink and the surface of the processor. Apparently having these gaps filled in by thermal paste helps keep the processor cool.

I'd also read on a site that if your computer does this (starts but nothing comes on the screen) and it's the processor that's the problem, there are a few symptoms. I can only remember one right now.

1: The computer blue screens.

This happened to me a couple of times in the two week period between me replacing my motherboard and my computer going back to not starting. In at least two cases, while a site was loading it blue screened. Normally, if a page on the internet loads too long, it just goes to "Not Responding" and I can end it in task manager. This time though, it just blue screened. And another time, I was playing a game while listening to a podcast. The computer just blue screened suddenly. I don't know if it was because my processor couldn't handle doing both of those, or if it blue screens for some other reason. When I'd get the blue screen, I'd turn the computer off and then turn it back on again and hope it doesn't happen again.

So yeah, I tried to turn the computer on one morning and it just didn't start. The blue light comes on, the fans start, the motherboard light lights up. The green light doesn't come on, the keyboard and mouse don't light up, and nothing comes onto the screen. I told my cousin, who I believe works with computers and who's built several computers some of this. Not anywhere near all this, but I told him about the motherboard light and the fans and such coming on and all that. He said that the processor burning out after working for two weeks due to me not replacing the thermal paste seemed reasonable.

So I've since bought a new processor and some thermal glue. They should be arriving soon. Even if it isn't the processor, the one I've bought is supposed to be better than the one I had, so it's an upgrade anyway. So just a few questions now that I've explained everything:

1: What do you think is the problem? Is it the processor?
2: Is there anything else I should know about thermal glue and how to apply it before trying to put it on my new processor and hook all that stuff up?
3: If it was the processor and the lack of thermal glue that was the problem, do you think the processor is just outright dead, or will it maybe function if I just put it back with thermal paste properly applied?

Some info on my computer:
Old CPU (which I've been calling the processor this whole time): [AM3] AMD PHENOM II X6 1100T BOX
New CPU (arriving shortly with thermal paste): AMD FX-8320 Eight-Core
Fan: CORSAIR H60 LIQUID COOLER BULK
RAM: [DDR3] 4GB DDR3-1600 SINGLE
Video Card: XFX HD6950 2GB VIDEO CARD
Old Motherboard (Pre-first breaking): ASUS M5A97, AMD 970
Current Motherboard: ASUS M5A97 LE R2.0
Power Supply: 800W POWER SUPPLY

[Calum]

4: He said something about it not being the video card, I can't remember why. It involved plugging something into something else, and afterwards still not getting anything on screen. So for that poorly remembered reason, maybe it isn't the video card.

There's nowhere else he could have plugged the display into, so unless he tried another video card, it remains a possibility.

5: The RAM sticks are properly connected, so maybe it isn't the RAM.

Just because they're properly installed doesn't mean one stick isn't faulty.  It's worth trying the memory one stick at a time, or downloading memtest86+ to boot from and test the memory.

6. When I put in the new motherboard, I had to remove the processor and attached fan. When I put it back in, I didn't put any thermal paste on the processor. I'd never heard of thermal paste at the time, and didn't know it was a thing. I noticed that the processor had some sort of glue residue on it, and just assumed someone had glued the processor to the metal thing attached to the fan thing for reasons beyond my understanding. I didn't know I needed to re-apply thermal paste (which I didn't have). The residue on the processor was only on a fraction of it.

You'll certainly need to reapply thermal paste to avoid cooking the CPU.  Best practice is to clean the CPU and heatsink with isopropyl alcohol and a clean, lint free cloth, then apply a dot around the size of a BB onto the CPU, in the middle.  Installing the heatsink then spreads the paste easily, and as long as you haven't put on too much, it won't come oozing out of the side or anything.

It's possible the CPU is dead, although I'd suspect the RAM or video card before that as CPUs very rarely fail.  I've built over 3000 PCs and tested/configured thousands more, and only ever seen maybe 2 dead CPUs out of the box, and a handful, maybe 5, die in use, and all from overclocking rather than overheating or general use.

[ExasperatedVulture]

There's nowhere else he could have plugged the display into, so unless he tried another video card, it remains a possibility.
Just because they're properly installed doesn't mean one stick isn't faulty.  It's worth trying the memory one stick at a time, or downloading memtest86+ to boot from and test the memory.

You'll certainly need to reapply thermal paste to avoid cooking the CPU.  Best practice is to clean the CPU and heatsink with isopropyl alcohol and a clean, lint free cloth, then apply a dot around the size of a BB onto the CPU, in the middle.  Installing the heatsink then spreads the paste easily, and as long as you haven't put on too much, it won't come oozing out of the side or anything.

It's possible the CPU is dead, although I'd suspect the RAM or video card before that as CPUs very rarely fail.  I've built over 3000 PCs and tested/configured thousands more, and only ever seen maybe 2 dead CPUs out of the box, and a handful, maybe 5, die in use, and all from overclocking rather than overheating or general use.

How do I download "memtest86+"? And also, how would I get it onto my computer? The only thing that starts are the fans and the blue light. None of the things connected to it (keyboard, mouse, monitor) get any signal.

As for testing one stick at a time, I'm assuming I'd do that by trying to start the computer after I've removed one of them, and if it still doesn't work, doing the same with the other stick. Is there more to it than that?

And for the record, the CPU is a year and a half old. I didn't know if you thought it was new from your "out of the box" comment, or if you were just talking about CPUs in general. When I moved it, there wasn't any thermal paste on it. There was a bit of residue, but it didn't really cover anything.

[Calum]

How do I download "memtest86+"? And also, how would I get it onto my computer? The only thing that starts are the fans and the blue light. None of the things connected to it (keyboard, mouse, monitor) get any signal.

Here's the website - http://www.memtest.org/
Download it (on another PC) and it'll be an ISO file.  Burn that to a disk, and boot from the disk.  I'm talking more after you get it to boot - trying one stick at a time would be the first step, Memtest would be to test the RAM installed to see if there are any faults.

As for testing one stick at a time, I'm assuming I'd do that by trying to start the computer after I've removed one of them, and if it still doesn't work, doing the same with the other stick. Is there more to it than that?

Nothing more to it, it's as simple as that really.

And for the record, the CPU is a year and a half old. I didn't know if you thought it was new from your "out of the box" comment, or if you were just talking about CPUs in general. When I moved it, there wasn't any thermal paste on it. There was a bit of residue, but it didn't really cover anything.

I was just talking in general, I understand the CPU isn't new.  I was saying that I've hardly seen any dead out of the box, and also hardly any have died later on.  CPUs nowadays have very good thermal protection built in and it's hard to damage them through overheating.