You can root the LG P999 and install a custom ROM on it. Rooting an Android device means obtaining root access; you are allowed total control over the file system of your phone. This is required for installing new ROMs and for many applications to work. Installing a custom ROM has many benefits. They can improve battery life, performance, customizability, and improve the UI. There are many custom firmwares being developed for the P999, such as Cyanogenmod and Weapon G2X. Follow the simple steps below

Read the tips and warnings sections before starting.

• Back up your device. Because your phone isn’t rooted yet, your options for backing it up are limited. I suggest using Paid apps on the Android Marketplace, which is all you need. We will be performing a much more thorough backup later once your phone is rooted.
• Install the P999 drivers on your PC. They will allow your phone to connect to your PC.
• Download SuperOneClick. SuperOneClick is a program that allows you to easily root your phone. Unpack the zip file and copy it to your desktop. NOTE: The file may be flagged by some anti-virus programs as it uses the same exploit to root your phone that an Android virus did.

There is more information and the download link in this thread: http://forum.xda-developers.com/showthread.php?t=803682

• Root your phone. This will void your warranty, so if something goes wrong you can’t return your phone. Make sure USB debugging is still enabled in your phone’s settings and connect it to your PC using the USB cable. Do not mount the SD card.
• Open SuperOneClick. Click the Root button. It will now check for your phone and root it if the drivers are installed properly. If this does not work, reinstall the drivers and make sure USB debugging is enabled on your phone.
• Back up your device again. Now that your phone is rooted, you can perform a much more thorough backup of your device using Titanium Backup. It’s free on the Android Market, so search for it and Select “Download”.
  • If you would like to support the developers and get some more useful features, you can buy Titanium Backup Pro instead.
• Enable USB Debugging. Titanium Backup will not work properly without this enabled and it is required for later steps. Go to Settings > Applications > Development, and select the “USB debugging” checkbox. Read the warning and select OK.
• Open Titanium Backup. Press the menu button on your P999 and select “Batch”. A screen with a lot of options will appear. Select the button beside “Backup all user apps + system data” that says “RUN”. Make sure “Kill active apps” is selected and press “Run the batch operation”. It will take a few minutes to complete.
• Copy the backup files somewhere safe. You can find where Titanium Backup saved the backup files by pressing the menu button, selecting “Settings”, and scrolling down to “Backup folder location”. You can either copy these files to your PC or an external SD card.
• Download your ROM of choice. There are many out there but it all comes down to personal preference. I use Weapon G2X. Make sure you get the P999/G2X version of your ROM, or it will not work. Copy the zip file onto your phone, and leave it packed.
• Install ROM Manager. This is a useful app from the Android Market that will allow you to easily boot into ClockworkMod Recovery to install your new ROM. Open it.
• Select “Flash ClockworkMod Recovery”. Scroll down the list of phone models until you see “LG/T-Mobile G2X”. Select it and allow it superuser permission if prompted.
  • NOTE: This will only temporarily install ClockworkMod Recovery. You will NOT be able to boot into it without going through ROM Manager again. Attempting to do so will instead perform a factory reset!
  • If you would like to install it permanently, follow the instructions here: http://forum.xda-developers.com/showthread.php?t=1056847
• Select “Reboot into Recovery”. This will shut your phone off and start ClockworkMod Recovery.
  • You can navigate up and down with the volume buttons and select options with the search button.
• Select “backup and restore”, then “Backup”. This will backup your current ROM onto your SD card.
• Wipe the cache partition, the dalvik cache, and finally do a factory reset.
  • The “wipe data/factory reset” and “wipe cache partition” options are found on the main menu, while “Wipe Dalvik Cache” is under “advanced”.
• Flash the new ROM. Select the “install zip from sdcard” option on the main menu, then “choose zip from sdcard”. Select the ROM you downloaded and put on your phone
• Reboot your phone. If the flash was successful, it should boot up into the new ROM.
• Restore your application backups. Download Titanium Backup from the market and copy the backup files back to your phone. You will have to change the settings in Titanium Backup so that it knows where your backup folder is. Press the menu button on your P999, select batch, and scroll down to select “Restore missing apps with data”.
  • It is not recommended to restore all your setting backups as this can cause problems when using a new ROM.

Note

• It is highly recommended that you have an external SD card before starting.
• It is possible to unroot your phone to restore warranty status, but don’t rely on that. Assume that you will not be able to get a replacement while following this guide and be careful.
• This guide is intended for Windows users. It is possible to root an Android using a Mac or Linux, but the procedure is different.

Warning

• Rooting your phone WILL void your warranty. There is also a small chance of bricking (permanently breaking) your phone. I am not responsible for any damage caused.
• This guide is for the LG G2X from T-Mobile in the US and the LG Optimus 2X from Wind in Canada, with the model number LG P999. It is NOT for the Optimus 2X sold elsewhere in the world, with the model number LG P990. They are very similar phones but unfortunately the ROMs are not interchangeable.