Ah! Well then

The first phase of the empire is usually reffered to as "The Caroligngian Empire" as that was the Dynasties name and also another way of pronouncing "Karling"

The Holy Roman Empire was, as you may have suspected, not in fact Roman but mostly German in culture with most of its emperors, or at least most of "The Karling Dynasty" were french

Charles Karling, also known as Charlemange was orginally rhe "King of the franks" and since he was buddy-buddies with the pope (Leo III?) the pope named him Emperor, on Christmas no less! A fairly good present if you ask me

Why did the pope do this? Well he was pissed off at the Byzantines (Although they still considered themselves Eastern Romans) and the orthodox faith in general as Catholicism and the Orthodoxy have always hated each other, buts thats a story for another day. Although it may also be because a bunch of Byzantine mercs troed to blind him and cut out his tounge.... 

Of course back then it was not really a empire just a alliance between the pope and a collection of unified frankish tribes while the true emperor of the romans sat in Constantinpole

Then all of a sudden shit starts to hit the fan and the Italians start pressing their claims on the empire and the Empire breaks apart with the death of Emperor Whats-his-face

A few years later there were a bunch of succsesion crisis's and the pope needs help once again so he says "Second time lucky!" and names a germanic king Otto I Holy Roman Emperor. This time its for real and is now actually a Empire, however still not Roman. Anyway It kind of backfires on the papacy as every Emperor after Otto dismisses the papacy at will. This pisses the papacy off to say the least and over the course of many years they bring a divide between Spiritual and Secular powers. Then in around 1070ish the Emperor sends a angry letter to the pope who reacted by saying "Well fuck you too!" and excommunicated the emperor. The vassals of the Emperor dont like this and a civil war breaks out, the emperor wins and elects a "Antipope", procedes to march on Rome and crowns his pope the true pope. Meanwhile the original pope is asking the Normans to take back the city and so the Normans come down from their beaches and do so. Except they got carroed away and sacked Rome :S

Gradually the empires power is dwindelled away by attacks from the outside, a divide of secular and spirtual powers, many civil wars and most importantly the ever increasing power of the Vassals. 

The end

Thats only a rough history of the first few hundred years and some of it is prbably wrong so you might want to check it