ATmega168A PU

Hello,
I'm quite new to Arduino, I have one Freeduino(16Mhz) and I use that to boot load other micro-controllers using ICSP pins.
I use ZF-007 ISP programmer to burn hex files of boot loader on micro-controllers. I've tried burning ALL boot loaders(given by Arduino for 168 controllers) on my new ATmega168A-PU, it writes flash memory successfully, but when I remove the ISP and attach USB cable on Freeduino, it is not loading.
I have read ATmega168A PU data sheet and for 4.5 to 5.5 voltages it supports clock with maximum frequency 20Mhz
I am not able to locate the problem which is frustrating.
Any help will be appreciated...

it supports clock with maximum frequency 20Mhz

The processor does but not the boot loader unless you get a special 20MHz one.

manoj_gudi:
but when I remove the ISP and attach USB cable on Freeduino, it is not loading.

Is there an error message?

Which board are you selecting in the Arduino IDE?