Dirty PC Fan

Do not ever let your computer get this bad. This will cause your computer to overheat. You will fry the CPU if you do not have enough air flowing out. These fans need to be cleaned.

Found this really cool website that has a "how often should i clean my computer?" Click here

I've browsed this website www.Computerhope.com and I've found a lot of useful information.

Fans are used to cool your computer down, it maintains air circulation. If they get dirty like the one in the photo, well you guess it. It will over heat and your computer will not work.
When the CPU over heats, your computer will automatically shut down to prevent it from overheating. When this occurs you NEED to clean your computer fans, get all the dust out of the fans, well pretty much everything inside needs to be cleaned.