disk space - Hard Drive Shows 122 GB used after fresh install of Windows, 18 GB of actual files?

I just installed Win 7, but did not format the drive. Windows shows that 122 GB of drive space has been consumed. Clearly this seems strange, so I selected everythign under the C: drive (including hidden) and only 18GBs is shown. Is there anyway to find out where the extra 100 GB went, and how to recover that space?

I deleted the Windows.old directory and ran disk cleanp already.

Thanks!