Hi,
As have been stated PM will not work on work on 64bit systems, you'll have to use MPASM which installs together with MPLAB.

The P16F876A.INC file is (should be) located in ...Microchip\MPASM Suite\ If you can't find the MPASM Suite folder and P16F876.INC file then there's somehing "wrong" with your MPLAB installation. If looking for the file from with MCS Open File dialog, make sure you set the file-filter to display all files as it defaults to .bas & .pbp files making the .INC files not show up.

64 bit compatibillity

/Henrik.