Vista upgrade ??

Right, basically i bought an advent 8111 from pc world in between the dates that entitle you to a free urgrade. I tried to upgrade this a long time ago through the tech guys website but i had to type in card details for the cost of delivery and accidently pressed back. I pressed forward and it didnt work. i then tried entering my windows product key again but as i had already entered it it would not alow me to go any further. I was trying to upgrade it again today but now i cant even find anything about the free upgrade on the internet is it too late now?