The temperature of the PC is heavily dependent on what software is running.
Mine will loaf along at under 50°C all day, unless I run the Volvo Ocean Race game. Then it gets to 80° and starts to complain.
I'd suggest a temperature monitor, and then watch to see what the CPU and/or HD temperatures do.
I particularly like Network Hardware Control aka nhc (yes, it IS a temperature and CPU monitor) - two little icons in the taskbar with the two temperatures.