Check the law in your state. Here in California, one cannot enforce a judgment until 30 days have passed since the judgment was entered. This gives the person who defaulted time to:
1. appeal or
2. move the court to set aside the default judgment.
If it has been longer than the time your state allows for enforcement and the defaulting party has not either appealed or moved to set aside (vacate) the judgment then they are out of luck. If not, go to the hearing on the motion to vacate the judgment and tell the court why it should not be set aside, ie. the defendant had no "good cause" not to appear at the trial, the defendant was properly served with your complaint (lawsuit or small claims action).
So how long has it been since you won the judgment?