Why didn't the Nazi surrender before 1944?

Nazi Germany was doing quite well in the West before 1944. It has practically all of Europe.

Two possible reasons:

1) Hitler did not want to surrender. He was a megalomaniac and "defeat" wasn't something he could tolerate.

2) Surrender meant surrender to ALL the Allies, not just the ones in the West. Stalin was holding the Western Allies to that. It would also mean giving Europe back to France, Belgium, Norway etc. Germany was living high on the plundering of those countries, and it wanted Norway's heavy water for nuclear weapons. Not even to defeat communism would those countries work with the people who destroyed their children and raped their economies.

Uhm, because they were led by Hitler who refused to surrender? Duh.

They had no reason to surrender.

Because they thought that they were winning

The Nazis were the most powerful entity in the whole world until the snow froze them to death in the Russian planes. 

They had no need to do so.

Until D-Day, they had no need to. The tide might have turned but they were far from defeated until then. The success of the allied invasion was by no means a forgone conclusion. Also Hitler thought their "wonder weapons" (esp V2 missile) would win the war and they might had they been able to produce them quicker and in large enough numbers.

By the time the V2 was ready, the Luffwaffe was virtually grounded due to lack of planes and fuel and the allies could bomb Germany with little opposition.

The German General Staff was afraid to buck Hitler. Something about going outside the chain of command.

Hitler felt that Germany's military failures meant it had forfeited its right to survive as a nation.

Actually they didn't surrender until May of 1945. By then they had suffered defeat at the battle of Stalingrad during which both Italian and Romanian troops surrendered. Berlin was being approached by the Russians from the East while the remaining Allies were approaching from the West. Hitler realized that defeat was imminent so he supposedly took his own life.