On MS windows
Power off your DSO203. Connect via USB cable to the PC.
Now, hold down the first button (play/pause) and Power on your DSO203. You should get the USB connected Ding-Dong sound.
A new drive will appear in your computer.
Copy the HEX file to the new drive
After the copy completes, you will hear the Dong-Ding indicating a disconnect
You can power off the DSO203 now.
On powering on again (without pressing the first button), you should be running the new firmware you downloaded (if it was a firmware for slot1)
To run a firmware meant for slot2, press button2 while powering on
To run a firmware meant for slot3, press button3 while powering on
To run a firmware meant for slot4, press button4 while powering on
Hope this helps.