how to transfer music from iPhone to new Windows 7 PC?

Howdy Itunes624,

Thanks for using the Apple Support Communities.

If you'd like to transfer the purchased music from your iPhone, you can follow the directions in the article below to learn how.

Re-download or transfer your iTunes Store purchases from an iPhone, iPad or iPod to a computer - Apple Support

Cheers,

Alex H.

See Recover your iTunes library from your iPod or iOS device.

tt2

Your iPhone is not a backup/storage device. You can transfer music from iPhone to iTunes: go to ~/Music/iTunes in your previous account (I presume you mean that you made a "new account" on your Mac) and copy all its contents to somewhere in your new account (not ~/Music/iTunes). Then drag the entire iTunes folder onto the iTunes app icon.