Hi, your problem is most likely the graphics card, Nvidia GO 7600.
Do you have no display but power and screen responds to touch?
The problem is known as the "Nvidia defect" were nvidia made load of GPU's with lead free solder, they have been taken to court about this in america and will cost the Co millions as its a major defect, get in touch with your retailer as this in a "inherent defect" (built with this fault) and you have 6 years from purchase to make a claim under the SOGA
Google "nvidia defect" and all will be revealed, this dosnt just affect HP's but countless other brands that had these faulty nvidia cards fitted.