If you already have it loaded on your new PC, MS Office 2007 is the way to go. Although there are many who have opinions contrary, it is the most popular Office tool. and MS Word is the most popular word processing program. You will probably be overwhelmed by the features in Word. Just take the tutorials to get you started. Don't worry about the features you won't be using.
If you don't have MS Office, you can download OpenOffice for free. Many people here at AW swear by it. I don't use it myself, because I'm used to using MS Word.