It is very important to backup your QT Wallet.
In order to backup your wallet you can do this either using the “Backup Wallet” Feature found under the “File” heading at the top left of the QT Wallet, remember to save the file that is generated to a safe place.
For advance users:
Go to Start > Run on your windows PC
Copy the wallet.dat file to a safe place.
In the event you need to restore this, you can drop the wallet.dat file in to this on your new computer and this will restore your wallet.