If you are asking a question like this, you need to find someone experienced to help you, or you are going to lose all kinds of data you haven't thought about but probably wanted to keep.
Stuff like browser bookmarks, your address book, downloaded email, etc, can all be tucked away in spots that aren't that obvious to a first time formatter to backup. Depending on where you may have bought music online, there are licenses in Windows Media Player that need backing up. You may have applications that require deactivation prior to the wipe (Adobe apps, some MS apps, etc), or they will be a pain to reinstall. Even your current wallpaper, if you set it from the browser, is not necessarily in an obvious spot in My Documents.
I'm in no way knocking your computer skills, but its a royal pain to go through the experience of discovering, bit by bit, all the little things you wish you'd backed up before the format.
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-Scott
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