My Great Idea: Somebody Had It First!

Dear Rich: I had this great idea for "something." I researched it online and found something that accomplishes the same thing but in a different way. It is has a trademark but doesn't seem to be patented. I am so upset because I thought this was a terrific idea and now I'm not sure if I can patent it. Can you help me? The short answer is that you can patent a device that accomplishes the same result as an existing invention provided that the manner in which it accomplishes that result is novel and not obvious to others in the field. For example, there are many ways to hold hair in place and no shortage of patents. An attorney would need to advise you about your particular situation since there's not enough information in your letter for us to provide much guidance.
Search on Your Own. You can certainly search the patent database to see if someone has registered a similar idea - we prefer Google's patent searching system over the USPTO database. And you can review the trademark database - lately we like Trademarkia.com more than the USPTO (although they each have searching idiosyncrasies). 
Great Ideas R Us. The Dear Rich Staff respects you for coming up with one great idea and hope you come up with more. But keep in mind, there's a reason for Thomas Edison's inspiration/perspiration equation. As Edison himself acknowledged, his success was primarily attributable to being a "hustler" rather than to any of the great ideas he instigated, cajoled or "borrowed." In other words, coming up with great ideas is not the hard part; the challenge is in selling your brainstorm.