How to make the Arduino look like an HID mouse device?

Hello, I'm working on an accelerometer based mouse project and right now facing some difficulties in making the Arduino appear as an HID device. From the playground section of the Arduino page, I came across this link http://hunt.net.nz/users/darran/ This link shows how to make the Arduino appear as a USB HID mouse device. The problem is that I cannot get the Arduino in DFU mode in the first place. The Arduino I'm using is a Roboduino which is shown in the following link: http://robokits.co.in/shop/index.php?main_page=product_info&products_id=319 Please specify where I can find the HWB line that has to be grounded along with the reset pin for this Arduino. Is it possible to get this Arduino to DFU mode? If not how else can I program the chip ATMEGA 168-20PU to behave like a USB Mouse ? Or is it better if I buy a UNO and then do the DFU programming part?

One more question that baffles me is once I upload the firmware for the USB mouse onto the ATMEGA 168 chip will I still be able to upload sketches onto the Arduino?? Because the bootloader program that previously existed must have obviously been overwritten right?

I'm sorry if my doubts sound silly. I'm just a new kid on the block. Please point out every single mistake of mine, I'd be grateful, thanks:)

You can turn the UNO and the Mega2560 into HID devices by reprogramming the atmega8u2 or atmega16u2 that provides the USB interface. The board you linked uses an FTDI chip for its USB interface, which cannot be reprogrammed.