Ouch. What makes you say that? I liked Win7 
Also, what don’t you like about the logo?
To answer your question: what makes a good logo? Creativity and Practice.
Here are some resources for you
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Well, there are two major criteria to judge a logo; they are branding and design. It is no doubt that the logo passed the branding criterion. As for design, I don’t think it is bad. It’s a competent design. So overall, it’s still a good logo.