trying to install snow leopard was supposed to have been installed by the computer department 2 years ago. it wasnt and i never noticed ( i know, sounds dumb).I tried to install myself, it went thru an hour long process. but I still have leopard

Bought an upgrage to Snow leopard from a big box electronics store and paid to have it installed by their "geek squad". But i never really checked it.I put the disk away and never thought much about again I was going thru my software and noticed that I had the Snow leopard version. Tried to intall it. I ran for an hour. It restarted twice thru the install. But when it was finished Leopard was still showing as my software version. Can anyone provide some advice. I have stertred the install again ( another hour) . Could my software be defective. any help would be appreciated