The National Debt and Budget

In the year 2000, the National Debt (US Gross Debt) was 5.674 trillion dollars. In regards to the National Budget in the year 2000, I remember that we had a surplus of 230 billion dollars in which of course could be used to pay down the National Debt. Now, in 2009, we have a national debt of 10.025 trillion dollars and we have a budget deficit close to 700 billion dollars. Now that the stimulus plan has been approved, our budget deficit will increase beyond 1.4 trillion dollars and by the end up this year, out National Debt will be up to 11 to 12 trillion dollars. So the question, how did we go from 5.674 trillion dollars in 2000 to 10.025 trillion dollars in 2009 in our National Debt?