thanks for taking a look at my problem mack. i have used the programmer with other chips and they work fine. the fact is just that the pic18f4550 oscillator settings for cpu and the usb peripheral is a bit complicated stuff even with the data sheet. the topwin software is from www.top2048.com. i have used it to program same pic18f4550 to turn on and turn off led at i second interval and it worked fine. i think the config for the usb peripheral is the major problem i am having. thanks again.