Hi, this is a simple one, just under 4 weeks ago I bought a used laptop of ebay from a company with good feedback who seemed to specialise in refurbishing this type of laptop among others (they sell a lot of them) and it came with a 14 day warranty. it has now developed a pretty major fault 
The laptop (Dell XPS M1730) has SLi 8800m graphics cards and the second one appears to have gone west, with SLI disabled it runs fine but if its enabled the laptop crashes either shortly after loading windows or straight away when a 3d game is loaded.
Do I have any ground to stand on with the sale of goods act? (I would prefer it be repaired as I like the laptop). Sorry if it seems like im whining but I didn't realise the warranty was only 14 days at the time I just concentrated on the returns accepted bit. And tbh I think its pretty reasonable to expect a £600+ laptop to last more than 4 weeks.
Thanks for any advice

The laptop (Dell XPS M1730) has SLi 8800m graphics cards and the second one appears to have gone west, with SLI disabled it runs fine but if its enabled the laptop crashes either shortly after loading windows or straight away when a 3d game is loaded.
Do I have any ground to stand on with the sale of goods act? (I would prefer it be repaired as I like the laptop). Sorry if it seems like im whining but I didn't realise the warranty was only 14 days at the time I just concentrated on the returns accepted bit. And tbh I think its pretty reasonable to expect a £600+ laptop to last more than 4 weeks.
Thanks for any advice