Slow Dell Latitude E6410 after multiple reformat attempts. Possible hardware failure?

Hi everyone,

 

I am having troubles with my Dell Latitude E4610 4GB ram Core I5 2.6GHZ. The laptop is pretty beat up; I broke the 320GB 5400RPM hard drive and replaced it with a 500GB 7200RPM hard drive. I have installed Windows 7 Ultimate 64 bit, but even after a fresh reformat, the laptop is very slow, almost unusable. After the installation of windows 7, it works fine for the first few minutes, and then slows significantly.  ">

I even tried an installation of Windows 8, still the same slow results

I have reformatted this machine several times with no success I have installed all the drivers necessary for the machine. I am beginning to think that this may be a hardware issue. According to Speedfan the CPU runs around 50 degrees Celsius on idle, which could possibly be quite hot for this machine. I have done the CHKDSK scan, the hard drive seems fine.

I am all out of ideas, what could be causing this computer to slow to a crawl? ">

What steps should I take to find the problem?

Any recommendations would be greatly appreciated.