Ok I copied this from xda forum by: Zecanills.
- You need to download the firmware of your device. Please check here the The_ERROR thread wich explains it very well:
[ROMS] Original LG Firmware list - xda-developers
- Download KDZ updater and uncompress it
KDZ_FW_UPD_EN.zip - 4shared.com - online file sharing and storage - download
- Install msxml.msi from the uncompressed directory
- Conect your device (do not turn on disk storage) and run KDZ_FW_UPD.exe (Has administrator).
- Select Type : 3GQCT
- Select PhoneMode : DIAG
- In KDZ file : Choose the ROM file you downloaded in the first step
- Press Launch software update and wait (It will be 10 minutes or so). In your phone it will appear "Emergency mode". Wait until it reboots.
And you're done!
This is what I did:
Basically on a windows machine you download kdz updater and uncompress it as it is a zip file.
This is what I did on an xp laptop.
I had to down load the drivers from the official lg site. when here you enter the code that is on the box the phone came in or under the battery.
Chose the your county and laguage from the drop down box at the top right of the dialogue box. Then from the middle you can choose the drivers. For some reason I had to find the files and click on them to install the driver.
Ok once you decompress kdz updater there are three seperate files to work with. 1. windows enabler. 2. msxml.msi 3.KDZ_FW_UPD.exe
You will also need to download the right file to restore with. For me being in Australia with 2.2 I needed V10a-00.kdz. You can find it with google.
Double click windows enabler and you will find an icon in the system tray at the bottom. Left click once and it will say on. Click and install msxml now.
Now you have to boot the phone into rescue mode. On Lg Optimus One turn phone off even if it means taking out the battery.
Press power - volume up - back (this button is next to the home button).
Connect to usb now. the lap top found new hardware and installed four drivers.
Then open device manager. Left click my computer - properties - device manager. You need to disable the lg modem driver. Left click on it and disable.
Now launch kdz updater. There will be a drop box on left set to 3gspt or similiar. on the right drop box set to diag. The long box just above the info box with a file at the side lets you browse to find restore file. e.g. V10a.00.kdz.
Double click the button below and let it do it's thing. My xp laptop is old and slow. Took 15min. My phone shut down and came up with an error at the last minute. Anyway I rebooted and all was good.
Everything was the way I left it. Just had to re-root.
My only real problem was getting the kdz installer to see the phone.
After installing the drivers restart pc. If it finishes quickly and just before saying finished it says phone not found try removing all phone related drivers including nokia pc suite and the lg suite and remove and reinstall the drivers.
It took a bit to get it right but it was worth it. How do you tell the wife your new phone is bricked?????
Anyway I going to install android on my main pc with virtual box so I can test everything before doing on the phone from now on.
Hope this is of some help to you.