Thanks Nav,

I tried it on a desktop and it works. But I think we are talking about different programming modes. Here is my rundown: (16F62X series)


Low Voltage Programming : MCLR is low(+ 5V) , MCLR is shorted to RB4 as
RB4 needs to rise to 5V also.

High Voltage Programming : MCLR is high(~ + 13V),
RB 4 has to be grounded



Voltages to Vdd of both modes are +5V. High voltage programming is better than low voltage programming in that all I/O pins can be used. (RB4 can't be used for LVP) But the downside is that it is harder to get 12 V source.