You can easily check temperature of your hard drive:
Type in command line:

sudo apt-get install hddtemp

When application Hddtemp is installed, you can use it typing:

sudo hddtemp /dev/sda

where /dev/sda is your hard drive.
It will output something like this:

/dev/sda: ST9120822AS: 40°C

You can also have a graphical applet on your panel which indicates temperature of HD. Type:

sudo apt-get install computertemp

Then:

1. Add “Computer Temperature Monitor” to your Gnome panel
2. Click right on applet icon and choose Preferences
3. In Display tab select HDDTEMP in “Select Sensor to monitor” and your drive in “Select Thermal Zone”.

There is another approach:
Install smartmontools package:

sudo apt-get install smartmontools

enable SMART monitoring (/dev/sda is a hard drive):

sudo smartctl  -s on  /dev/sda

and execute this command:

sudo smartctl -a /dev/sda | grep Temp

it will output something like:

194 Temperature_Celsius     0x0022   040   048   000    Old_age   Always       -       40 (0 22 0 0)

40°C is the temperature of hard drive