UPDATE: I'm guessing you installed Activestate Perl and then installed Activestate 64-bit Perl without removing the first installation; hence the two paths.

On Win7, you can remove the unwanted one by right-clicking "My Computer", selecting "Properties" and selecting "Advanced system settings". In that dialog, press "Environment Variables..." button and in the "System Variables" section of the new window, "Edit..." the "Path" variable.

Alternatively, don't do anything as Windows - like most other OS's I know - searches the path in order so it will find (and run) the perl.exe found in C:\Perl64\bin and never make it to the C:\Perl\bin directory.