Here is how to flash a USB nand reader, because the tutorial was hard to follow on the website.
Use this tut if you have this little guy:
[ Register or Signin to view external links. ]

First download this stuff:
USB Microchip Hex file loader/ Driver
[ Register or Signin to view external links. ]

Hex files for PIC FLASH (Xbox 360 nand)
[ Register or Signin to view external links. ]

Special version of Nand pro with drivers
[ Register or Signin to view external links. ]

Step one:
Put your nand reader in bootloader mode. There is a little black plastic tab, move that over.

Step two:
Plug it into the computer with no cables attached other than USB.

Step three:
Click to install your own drivers (advanced options)
find your drivers in program files
[ Register or Signin to view external links. ]
The folder should be named MCHPFSUSB so use that location as the folder that has your drivers.
This is your driver:
[ Register or Signin to view external links. ]

Step four:
With the driver installed, open up the Picdem USB tool
[ Register or Signin to view external links. ]

Step five:
Load your HEX file called PICFLASH

[ Register or Signin to view external links. ]

Click on the drop down menu again, and select the HEX file again or it won't work.
Then, click program device!

Step six:
Unplug your USB SPI nand reader and disable bootloader mode
Plug it back in

Step seven:
Repeat step three, but instead use the .INF file located in the Nandpro folder you downloaded
It is in the top left corner in the pic below and is called custom.inf
[ Register or Signin to view external links. ]

Finish the wizard.

Congradulations, you have flashed your USB nand reader and can now jtag your Xbox. It will work with JTAG tool (by coolshrimp) too.