[SOLVED] I have solved the problem and thought it would be nice to give my solution here in case people have this problem in the future. The hardest parts were to get my laptop to recognise the cube and install the Rockchip USB driver.

Equipment list

Cube U30GT2

Download and install RKBatchTool.exe V1.6

Download preferred ROM file (.img)

My laptop with Windows 7 home premium, 64-bit system

Quality and reliable USB cable from my Sony camera

Instructions

1. Connect one end of USB cable to Cube only.

2. With the Cube OFF, press and hold Vol+ and power buttons together then connect the other end of the USB cable to a USB port of laptop, Windows should then pop up a message "Windows installing software driver".You can now release your fingers from the Cube. After about 15s, if Windows cannot find the driver, it will display a message "Device driver was not successfully installed".

3. Goto Control Panel - System - Device Manager and look for "Unknown Device" with a yellow exclamation mark next to it.

4. Right click on it and choose "Update driver software".

5. Choose "Browse my computer for driver software" and then select the driver from the following folder on the laptop:

RKBatchTool v1.6 - Rockusb_v3.0 - Rockusb - x64 - win7 - rockusb.inf

Note: x64 means 64-bit system, x86 means 32-bit system.

- Wait for Windows to install the driver.

- If successful, you can then use RKBatchTool to flash the ROM file into the Cube by following the instructions from the link below which is relatively easy to perform:

http://liliputing.com/2013/03/cube-u30gt2-quad-core-tablet-gets-firmware-update-custom-rom-treatment.html

I was able to flash the ROM file into the Cube with no problems.

Important Notes

- I had a lot of problems in steps 2 to 4 above and spent about 1.5 days of trying. Sometimes, I couldn't get "Unknown Device" in Control Panel. I had to connect to 3 different USB ports on my laptop in order to trigger "Unknown Device" in Control Panel. Therefore, you have to be methodical and patient. You may need to repeat the above steps many times to get it to work. You may need to reboot your computer after a failure.

- When I got to step 5 once, it wouldn't accept the same driver within RKBatchTool.exe V1.7 folder so I chose RKBatchTool.exe V1.6 which worked for me. It could be me!

- In step 2, I NEVER got "Found New Hardware Wizard" when I plugged the USB cable into the laptop.

- Before I got the above to work, I tried downloading Moborobo to use its driver to communicate between the Cube and laptop which the laptop was able to access the folders of the Cube. However, when I tried to use RKBatchTool V1.7 to access the Cube, it failed to recognise the Cube meaning flashmode couldn't be entered. Therefore, you may not need Moborobo.

- Ensure that you read the above notes and other threads carefully before flashing the Cube.