Set MCLR to OFF, so it is an I/O pin, (otherwise you need a 5K resistor from MCLR (GP3) to +5V). Depends on your application. Do you need RESET? If not, then disable it and you get another input to use (GP3).

CMCON = 7 ' this turns the COMPARATOR off
ANSEL = 0 ' this turns the A/D convertors off

And don't forget that if you decide to use GP3 it is INPUT ONLY.

BTW - ALWAYS read the Datasheet!!! Look at the first few pages where is shows all the functions for each pin (especially the pin that is causing problems). If there are more functions than just "I/O" then you MUST go to those sections in the datasheet to see what the defaults are. Usually I/O is NOT the default. It's a little tedious at first, but saves a lot of headaches later. And usually you will find the answer quicker than asking here (but when you are really stuck, this forum is a life saver).

regards,
Jim