Once you have published it, regardless of where or how, you will never have the ability to offer "first publication rights" again. And why is that a big deal? For most publishers, if you have already published and didn't sell enough copies to stir up any real interest, then they are not going to waste their money on trying to sell it. You've already demonstrated it won't sell. So what other options do you have?
The first option is to go ahead and shop it anyway. If you feel your book is good enough to become a hit, then give it a try. The publishing houses aren't going to know that you published it and gave away all your copies. If you end up stirring up any interest and it gets to the point where they are willing to discuss contract, then come clean and tell them what you did. If they really liked your book, they are much more likely to agree that your efforts did not constitute a true attempt to sell the book.
The second option is to self-publish as an e-book. Since you already have the book written, all you would have to do is convert it to the proper format and submit it to a distributor. This won't cost you a penny to do, but now you will be responsible for promoting and marketing the book. Not an impossible task, but it can be time consuming.
The thrid option is to self-publish in print through a company like CreateSpace. I suggest them because you can set everything up for free (you do have to pay for a proof copy, but you'll probably want your own copy anyway). If you want to expand your distribution channels to include book stores, it will cost you about $40, but aside from that and the cost of the proof copy, you're not out much money. Again, however, you have to do the promoting and marketing.
Of course, you can always combine options two and three, depending on what you really want to accomplish. If you go with a publishing house, you may spend months shopping it around, then another month or two agreeing on the contract, and then 12-18 months waiting for it to be printed and distributed. If you go with either of the other options, you can make it available within 3-10 days.