Synchronize ERASE iPAD

Did you include your iTunes library with your computer's backup along with all other important data such as documents, photos, etc. before reformatting your computer's hard drive?

First you need to re-authorize your computer with your iTunes account with iTunes if you haven't already done so.

With your iPad connected and without syncing, at the iTunes menu bar go to File and select Transfer Purchases From - the name of your iPad.

Since you are Windows sufferer and are forced to re-format your hard drive and/or re-install Windows far too often (I've never had to reinstall OS X on any of my Macs over the last 10+ years), you need to de-authorize your computer first. The 3 authorized computers are probably the same computer. Regardless, once you reach 5 authorized computers you can de-authorize all from an existing authorized computer (this can be done once a year) followed by re-authorizing the computer or computers you want or need authorized.

Since you didn't include your iTunes library with your computer's backup, your iPad will be erased of all iTunes content the first time you sync your iPad with iTunes on a new or different computer. By reformatting your computer's hard drive and re-installing Windows, your computer is detected as a new or different computer which has nothing to do with your iTunes account and re-authorizing the computer with your iTunes account.

The difference now is all iTunes content on your iPad is now in your iTunes library and can be re-transferred to the iPad.

For future reference since this won't be the last time you have to re-format your computer's hard drive and re-install Windoze, check this link with instructions for backing up your iTunes library. Backing up and re-storing your iTunes library this way will prevent this the next time you reformat your computer's hard drive.

http://support.apple.com/kb/HT1751

The warning message is in regards to your iTunes library only. This includes any music, movies, tv shows, and apps purchased/downloaded direct from the iTunes store with your iPad which should now be in your iTunes library.

Emails, notes, and photos are not in your iTunes library.

20GB of photos came from where? Photos in the Camera Roll can be imported by your computer as with any other digital camera.

After transferring all iTunes content from your iPad and importing the photos from the Camera Roll, right-click on your iPad under Devices in the iTunes source list and select Back Up from the menu window provided.

Follow this by restoring your iPad with iTunes from your iPad's backup. After the backup is restored, select Sync Apps under the Apps tab and the same for music under the Music tab for your iPad sync preferences with iTunes making your selections below these tabs followed by a sync to re-transfer your selected iTunes content - namely the apps. As long as the email account is an Exchange or IMAP account, all email should remain on the server.