avrdude: verification error, first mismatch at byte 0x0000

I am unable to program my Arduino older NG (ATmega8 ) I am using Arduino 1.0.1 also 1.0.5 also 0021 but still not getting the response I have checked the comports and drivers Its all perfect also selected proper board and comport and i am getting the following error;

avrdude: verification error, first mismatch at byte 0x0000
0x3f != 0x00
avrdude: verification error; content mismatch