Hard drive shutting down noises and CPU slow

[guandra]

I just change most parts of my computer over a month ago. I installed a new video card (Asus EAH3870), motherboard (Gigabyte EP45C-DS3R) and new RAM (4GB DDR2 patriot PC2 6400). I also bought a Thermaltake TR2-550W.

The only things left are the main hard drive (over 2 years old, Maxtor STM3160215AS ATA device), a second hard drive to storage files like videos and music (over 4 years old WTC WD800JB-00CRA1 ATA device) and the processor (Intel Core 2 Duo E6550 @ 2.33GHz bought over a year ago).

My computer since I bought the maxtor hard drive 2 years ago made a noise of shutting down but it never turnned off. Everything kept working with no problems and it never worked slow. But in the last month, every day after a few hours of working (I use it mainly to write documents and run statistical software like SPSS and Excel) the computer starts working really slow. It take at least 20 second to run anything. And this afects everything lately, running firefox, windows media player. It still makes the shutting down noises, but lately its running slow also.

what might be the problem? can it be the hard drive?

Thanks

[not important]

Run the manufacturer's diagnostic software on the HDD's. Your problem sounds more like overheating and the CPU is throttling back. Check your temps when you first boot up and again when it starts to slow down.

[guandra]

I runned the diagnostic software and it found no problems with the hard drives.

I check the temperature: it normally around 47ºC and when I put the computer to work different programs at the same time it go to 58ºC. I'm not sure what's the acceptable temperature, but it never went over 58. Actually, the computer freezed once and I had to rebbot, but the temperature was 49ºC when this happened. What can be the problem?