To do an HDR you don't have to take everything and turn it upside down to come up with a good HDR photo. I have quite a few HDR photo's in my 365 that are not 'upside down" You can take a photo and "tweak" it with HDR and still have it look somewhat normal.
As your photo, your first mistake is you said you used an old photo, (just one image). So I'm not going to comment more than that for now. You're going to get better results if you bracket three photos. In your case this is going to be a little harder for you because the D3100 does not have an auto bracket feature.
Your going to have to get out your tripod, make sure it's good and tight when you get your shot lined up. Take at least three photos. One at normal exposure, one two stops under exposed (-2.0) and one over exposed two stops (+2.0). Your going to have to change your exposure by hand, this is where the tripod is important, you don't want to move your shot, HDR software WILL pick up on this if the shot is not line up close. Some software has an auto alignment feature. All my HDR shots have been hand held, but I have an auto bracket feature on the D90 and get three shots off in under a second, and my software has the auto alignment feature. So I can get away with it (sometimes).
Don't know what software your using for HDR, I would suggest Photomatix Pro. It can be downloaded with a 30day free trial.
I have found HDR loves broken skies with dark and white clouds, rust, and some shades and shapes of red or brown brick. HDR Black and White is neat too but I have not mastered that one yet. Not every photo is a candidate for HDR, it's either going to work or it's not.
Taken my advice and start over. You'll be much happier with the resulsts.
Welcome to HDR
Rick