iTunes and reinstalling Windows

There is an iTunes folder in your my music. That is where the iTunes database and all your music is. Just copy it to an external.

 

The above answer should do this for you. I assume you didn't change the default directories where iTunes saves your media. Just copy the entire install over.

 

Indeed.

The "iTunes" folder in:

C:\Users\YourName\My Music\

Should contain all of the content that is in your iTunes library.

To make iTunes move all of your library content to that folder (if it's not there already), go to:

File > Library > Organize Library

... tick the "Consolidate Library" box and click "Ok".

When you reinstall, just put that folder back in the same place (i.e. C:\Users\YourName\My Music\).

Before you format, you should also deauthorize the computer:

http://support.apple.com/kb/HT1420

See the "To deauthorize a computer" section.

 

Yes putting your music on an external is the best way to go. You should always have your music backed up an external drive just in case your computer crashes. As to your phone. Once you got iTunes back up just plug in your phone usb and it should back it up like normal and you shouldn't lose any thing. Oh and by the way make sure you are logged into the same iTunes account as your phone and everything else as stated above should work. Hope this helps.