How to Become a Millionaire with Only $10,000

So I am taking FIN 300 (Intro to Finance for all non-finance majors) right now.  The other day, my professor told us that there are three ways to get rich:

1. Marry Money
2. Inherit Money
3. Invest Money slowly over time

So how does that work for me: 

1. Marry Money--Since I'm already married and have merged bank accounts with my wife, I've pretty much maxed out this option.  
2. Inherit Money--Being the youngest child, my claim on the "birthright" is pretty non-existent.
3. Invest Money slowly over time--This seems to be my best shot at becoming a millionaire so I found a website that will show me how to do it.

To see how it's done, click the link and then enter the information below: How to Make a Million with Only $10,000

Enter the Following: 

• Ending Value: 1000000
• Beginning Value: 10000
• Number of Periods: 40 
• *A period is generally considered to be a year

Thus, with a principal investment of $10,000 at age 25, with compounding interest, I should be a millionaire by 65!

Anyone see a hole in my plan?  Help me out you finance majors.