If there was no DWI conviction on the first charge, then it cannot be used to enhance punishment on a second arrest. The second arrest would be a DWI first. (However, the prosecutor making an offer who sees that there was a prior DWI that was dismissed or otherwise not prosecuted will likely up their offer to something more than a first offender might receive.)
Although I have answered the question to try to help you, you should consult with a lawyer in your area in person on the matter. In addition, my answer does not establish an attorney-client relationship between us.
It will not be used to enhance you to a DWI2nd and the punishment range associated with a Class A Misdemeanor but the terms of your probation will likely be a little more stringent than a real first time DWI offender because the ADA will know of your prior situation most likely.
If you are facing a DWI you need an attorney.
Although my intent in answering this question is to aid you in the legal process, my answer does not establish an attorney-client relationship in any way. You should seek the advice and counsel of a qualified attorney in your community to evaluate your legal needs and to advise you. No Attorney-Client Relationship is created without the specific intent of both parties.