If you are not using PHYLock and you attempt to image the Windows partition while Windows is running, you will be warned that the partition cannot be locked. You can ignore this warning and continue, but the only way you can be sure a partition being backed up is in a consistent state is by having it locked or by using Image for DOS, Image for Linux, TBWinRE, or TBWinPE. (Your purchase of Image for Windows includes Image for DOS and Image for Linux.)
If you're using WinNT/2K/XP/Vista or Windows 7/8.x/10, you can use the PHYLock utility to maintain the consistency to a "point in time" even on the system partition and even with Windows running. In short, if you plan on imaging an unlocked partition from within Windows, use of PHYLock is strongly recommended.
Microsoft's Volume Shadow Copy service (VSS) is also an option if you're using a version of Windows that supports it (Windows 2003 or later). Enable the Use VSS When Available option in Image for Windows.