It might be important, at some point, to know what your computer really is. The "lshw" tool tells you the truth about what do you have in hand. This tool also can be filtered by components such as memory, disk, graphic or network.
To get all specs for your computer simply type:
sudo lshw -C memory
To see the status of your memory, simply type:
sudo lshw -C cpu
sudo lshw -C disk
sudo hdparm -I /dev/sda
You might have to run: sudo fdisk -l to find out where your drive is.
sudo lshw -C network
lspci | egrep 'Ethernet|Network'
sudo lshw -C display
lspci | egrep 'VGA|Display'
Is there any discrepancy between what the sales men told you and the computer specs?