Keys are sometimes stored in the Windows Registry. You can navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Corel (or Ulead) to find serial details.
By 2009, Corel decided to streamline its product line to focus on . They officially "retired" PhotoImpact, leaving X3 as the final, frozen-in-time version of the software. The "Key" Dilemma photoimpact x3 key