http://www.razersupport.com/index.php?_m=down...p;nav=0,11
You have to install the razer deathadder drivers first.
and follow these steps to update firmware:
1) Unpack the zipped file and double click on the "DAFirmwareUpdater.exe" Press “T” on the keyboard to select “No, not this time” Then press “N” to proceed.

2) Press “N” on the keyboard to proceed when you see the next screen.

3) Press “C” to allow windows to complete with the firmware updater.

4) “Enter” to complete the installation.

5) Once the updater is done, your Razer DeathAdder firmware has been completed.