Thanks for the quick answer by the way some more questions from a newbie.
my wallet.dat have inside of it all my address?
If I have a backup right now of my wallet(With no BTC) and if tomorrow I receive my money imagine that after I received my money I have to format the OS will I loose the money or it will get all the block chain and get the money again?
If you're paranoid, backup your wallet after every time you *send* money.