How can I upload bootloader to the usbserial chip Atmega8u2 on Arduino UNO

I have an arduino UNO R2 and an AVRISP programmer, I used the AVRISP to overwrite the bootloader of atmega8u2 with UNO-dfu_and_usbserial_combined.hex. then I find a device named Arduino Uno DFU, but I can't install its driver. Is there somebody to help me solve this problem. Thanks a lot!

Levi008:
I can't install its driver.

Could you expand on this? What have you done to install the driver so far, and what are the symptoms telling you that the installation failed?

PeterH:

Could you expand on this? What have you done to install the driver so far, and what are the symptoms telling you that the installation failed?
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It's no longer a problem now. I used the Duemilanove usually, what I yesterday do is to find the driver path(arduino-1.0.1\drivers),and install it just like I do with FTDI chips.

My computer system is WIN7,and what I need to do is just to power off the UNO,and replug to the computer. and it will install the driver itself, then the USB device will turn to a serial com(such as COM7).
The reason I do this experiment is because I see that UNO has some function such as keypad,mouse,MIDI device which the Duemilanove does not have.
Are there some projects or tutorials to teach us to do with these added functions?

The reason I do this experiment is because I see that UNO has some function such as keypad,mouse,MIDI device which the Duemilanove does not have.
Are there some projects or tutorials to teach us to do with these added functions?

Is there anybody to give me some tutorials?

The atmega8u2 here is just used as USB Serial Adapter.

Maybe you can watch this [u]http://arduino.cc/en/Hacking/MidiWith8U2Firmware[/u]