i have to do something about my windows 7 ultimate. at first i installed with no problem. i remove that small file ecfg and choice 7 ultimate. i use the key i purchase on ebay and ''perfect"" months later say counterfeit and i have a black screen, windows still running, but no as before. well: is better if i formated my hard drive and reinstall with the same key ( i don't have another) or i can do a modification to this one. please any advice should be step by step, because i am not a pro. waiting for your help. thanks.