[GT540 Optimus General] mistermentality:
This is a guide I followed from another forum, and posted elsewhere with some minor additions in case anyone had problems.

The guide is from a forum post at the android forums,it is NOT my work, the added bits are mostly what I have found from browsing here and from asking questions. While I can't be held liable if you mess your phone up having done so myself I thought this could helpa few people and save them searching various threads for answers so hope it helps :)

The guide

To install this ROM you need to have fastboot enabled on your phone. If you have Android 1.6/2.1 installed from LG, then fastboot is not enabled. I will explain how to enable fastboot on your phone (this involves re-flashing/replacing your currently installed firmware):

I am unable to post links yet so you will have to copy and paste the appropriate link into your browser replacing the ** with tt

KDZ Updater Carphone Warehouse Unlocked.zip can be downloaded at h**p://goo.gl/7aRTc - A link to a zip archive with all the files needed to flash to Android version 2.1 with fastboot (Carphone Warehouse Unlocked)

KDZ Updater Europe Open.zip can be downloaded at h**p://goo.gl/BOcYT - A link to a zip archive with all the files needed to flash toAndroid version 2.1 with fastboot (Europe Open)

Download the version that best applies to you, if you live in the UK, I'd recommend you download the Carphone Warehouse Unlocked version, whereas if you live in Europe, I'd recommend the Europe Open version (simple right? )

I live in the UK and used the open rom from Europe as the Carphone Warehouse rom would not install

Now, how to flash these versions; I'll explain in detail how to flash the ROM's from starting with backing up.

Instructions to install ROM with Fastboot:

1. Before you start, make sure you backup all your data by installing the z4root.1.3.0.apk file onto your phone, then open it and choose 'Permanent Root'. Your phone will root and reboot. Then go to the Market and install 'MyBackup Root', open it and do a backup of your apps and personal data (contacts, sms, call log etc.) Once this is done, go to Settings>SD Card and Phone Storage>Unmount SD Card, a notification in the notification bar should appear saying 'SD Card safe to remove'. Remove the battery cover and remove the SD card and store it in a safe place. Then continue to step 2.

2. Extract the .zip file you downloaded to your computer (e.g. your desktop). Open the folder and install MSXML 4.0 SP3 Parser (msxml.msi).

3. Once that has finished, install LGAndroidDriver_WHQL_ML_Ver1.0_All_Win7.exe which are the drivers so your computer will recognize your phone.

4. Next, open KDZ_FW_UPD.exe

(i) Change 'Type' to '3GQCT' *THIS IS A MUST, THE UPDATE WILL NOT WORK OTHERWISE AND YOU MAY BRICK YOUR PHONE*

(ii) Make sure 'PhoneMode' is set to 'DIAG'

(iii) Browse for the 'V20B_00+Fastboot.kdz' file.

5. Prepare the phone by enabling USB Debugging by going to Settings>Applications>Development>Enable USB Debugging and connect the phone to the computer via USB cable and wait for the drivers to install for the phone.

6. Click 'Launch software update' and do not use your computer until the update is complete. The update will take roughly 10-20 mins to complete.

If you have a problem with this try a different rom, this guide offers two to choose from.

Instructions to install CyanogenMod:

Once the update is complete, your phone will reboot, what you need to do is power off the phone and whilst the phone is off, press and hold the 'Camera' button all the way ANDpower on the phone, make sure you hold the 'Camera' button. The phone will display the LG logo and disappear, then display a blank screen. The phone is now in fastboot mode!

Now you want to download this file: Flashing CyanogenMod.zip and extract it to a folder called 'Android' (without the quotes '') on the C: drive (you'll probably need to make this folder yourself.

1. Now open CMD with administrator privileges (Search for CMD in the start menu and right click on 'cmd' and click 'Run as Administrator' )

2. Connect the phone to your computer via USB cable and wait for the necessary drivers to install.

If when connected with a usb cable the computer says "waiting for device" and nothing else happens try installing the fastboot drivers. You can do this by going to the control panel of your pc, from the Windows start menu, opening the list of devices and where you see the one representing your phone (likely, as was the case with me, it will say android and have a yellow exclamation mark over it). Different versions of Windows do things slightly different but what you need to do is simply update the driver by choosing the icons properties box choosing UPDATE or INSTALL DRIVER and when asked pointing it to the folder where you unzipped the drivers.

3. Then go back to the cmd window and type:

Code:

cd C:\Android

(i) Then type:

Code:

fastboot.exe -w

(ii) Once that's completed, type:

Code:

fastboot.exe erase system

(iii) Once that's completed, type:

Code:

fastboot.exe flash system system.img

(iv) Once that's completed, type:

Code:

fastboot.exe flash boot boot.img

(v) Once that's completed, type:

Code:

fastboot.exe reboot

4. Your phone will now reboot with CyanogenMod 6.1.1 (Android 2.2.1). The first boot might take longer than a normal boot.

If your phone stays at a blank screen you simply forgot to do one of the above steps, in which case simply repeat them. It is likely if that happens that you simply forgot the flash boot image instruction.

5. You can now re-insert your SD card and go to Settings>SD Card and Phone Storage>Mount SD Card

Enjoy!

The instructions for flashing both the firmware with fastboot and flashing CyanogenMod are included in the zip archives called 'Readme'. I'll update the links so that you'll always have the most up to date version of CyanogenMod available for download, note that if you choose to update your phone you will loose all your data including apps etc. so backup before you update

And that, with a few comments added by myself, is the guide.

Once you have set your phone up the way you want power off your phone. Hold the HOME and POWER buttons down while the LG logo appears and you will see a menu appear on screen.

Using the volume down key to navigate the different menu choices, and the camera button to select an option choose the BACKUP OR RESTORE option and from the sub menu that it will give you choose BACKUP.

This will make a backup of your phone AND all your data, if you ever mess up an update or think you have damaged your phone in the future simply holdthe POWER and HOME buttons down and when the menu appears choose the RESTORE option :)