Which component is powering down my computer?

[tokyotech]

The Problem

I have a 5 year old desktop computer that has served me well up until last week. Things started becoming very slow. Going into a folder, opening programs, hovering over buttons, maximizing programs would all freeze the computer for a minute. However, the mouse was still movable while the programs freezed. Starting yesterday, it would crash and reboot the computer after an hour of use (happened 3 times). Sometimes it was during watching a video in VLC (with GPU decoding off because VLC doesn't work with my ATI card), listening to music in Soundcloud on Firefox, or uploading photos to a social network. The screen would become interlaced and the horizontal lines of pixels would get skewed in random directions. If there was music playing, the music would jumble up like a robot dying (think Transformers iconic transforming sound). The crashings would take about a second.

Attempted Fix

I thought the slowness was caused by severely fragmented harddrives. I hadn't defragmented in 2 years, so I told Windows to defragment all my 5 drives. After about 16 hours, all drives were defragmented, but I still experienced the same sluggishness.

Possible Cause

The only new thing I started doing recently was playing the newest Tomb Raider with the default medium settings. MSI Afterburner would report the GPU temperature consistently go to 100 Celsius. I have the GPU set up to increase fan speed as temperatures increase though. Maybe I fried parts of the GPU.

System Specs

• 
  ■Windows Vista Business 64 bit
  ■SAPPHIRE Vapor-X 100283VX-2L Radeon HD 5770 (Juniper XT) 1GB 128-Bit GDDR5 PCI Express 2.1 x16
  ■Intel Wolfdale Core 2 Duo E8400 @ 3.0 GHz
  ■3 internal and 2 external SATA harddives (mostly 7200 RPM high performance models).
  ■GIGABYTE GA-P35-DS3L LGA 775 Intel P35 ATX All Solid Capacitor Intel Motherboard
  ■ENERMAX Liberty ELT500AWT 500W ATX12V SLI CrossFire 80 PLUS Certified Modular Active PFC Power Supply
  ■G.SKILL (4 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model F2-6400CL5D-2GBNQ

I've only upgraded the GPU after my GeForce 8800 GT died. I've added about 1 harddrive per year.

 

[RaDiKaL_]

Overheating will indeed cause a system to slow down. Since how long haven't you cleaned up inside your case? for that GPU reaching 100ºC the fan must be practically not working at all, give a good cleaning in there, I also wonder about your CPU temps, finally, the problem you're having could also be caused due to a failing HDD.

 

[Geef]

I agree with RaDiKaL about the GPU, it should never get to 100, maybe 90 tops. Get a can of air and get all the dust out and see if thats the problem. Or do what I do when the can of air is empty. Drag machine to the garage and use the air compressor.
I don't think a failing hard drive would be the problem if you were able to do an entire defrag. Those do take a TON of time if you haven't done them in a while.

 

[tokyotech]

Cleaning

I probably haven't cleaned the inside of the PC in 3 years. I just opened it and vacummed it up. There were huge dust balls and spider webs.

Graphics Card

The PC never crashed while I was playing the game. I never dared playing games after the first slow-down and crash. When I'm not playing, the temps are low - I forgot the exact temp, but I remember it was much lower than my old-school nVidia Geforce 8800GT.

Can a GPU really crash the computer? I thought the GPU is just responsible for display. If the GPU is broken, wouldn't it just jumble up the graphics and not crash? I had a similar experience with my nVidia Geforce. It would display random geometric shapes and lines in bright magenta and green on the screen. All the while, I was still able to use the computer (in the parts that I could still visually grasp).

Harddrive

I removed all internal harddrives from the PC and tested each on using a dock on my Macbook. Since Macs can only read (but not write) NTFS drives, I only browsed through the files. I didn't have any problem playing videos on those drives.

 

[Geef]

A long time ago I had a video card that started going bad and I remember starting to get lines on the screen and sort of like an old tv screen with bad reception. That card ended up dieing and I think it was because of heat because I could run the computer for a little while just fine then after a little while it started doing that. The computer never crashed or had errors because of it.

Now that your computer is cleaned out you should probably run programs that keep an eye on the CPU and GPU temps.