|Your CPU appears to be overheating. Is the CPU fan turning fast? Is the inside of the case full of dust & tint? Blow it out using compressed or canned air. When blowing out, do the power supply from both ends. This will be messy so you may want to take the case to a location where the dust won't be an issue.|
DO NOT vacuum it.
BTW, Your memory is the RAM (Random Access Memory). The 640GB is obviously the storage capacity of your hard drive.