Android 4.2.1 Jelly Bean
CM10.1 Jelly Bean ROM based on Android 4.2.1 is available for Samsung Galaxy S I9000.

Samsung has ended official updates for the Gingerbread version of its mobile Android operating software for the Galaxy S and followed that with a similar finish for the Jelly Bean version. Fortunately, independent developers continue to offer updates with custom ROMs. XDA developer matt73300 has released a CyanogenMod 10.1 custom Rom for the Android 4.2.1 (Jelly Bean) version, for the Samsung Galaxy S (I9000).

Galaxy S users looking to upgrade to Android 4.2.1 CM10.1 (Jelly Bean) firmware may follow this tutorial below. IBTimes UK reminds its readers it will not be responsible for damage to the device during this procedure. In addition, users are advised this method is only for the Samsung Galaxy S (I9000).  

Pre-Requisites

    • Ensure back-up of all important data
    • Ensure battery has at least 80 percent charge
    • Ensure device is factory unlocked
    • Ensure device is rooted and ClockWorkMod (CWM) Recovery is installed   

To Install Android 4.2.1 CM10.1 (Jelly Bean) ROM on Galaxy S (I9000)

    • Download Android 4.2.1 CM10.1 ROM (Find alternate link here)  
    • Connect device to computer using microUSB and copy above files to internal storage
    • Disconnect device from computer and switch it off
    • Enter Recovery mode 9to do so, press Volume Up, Home and Power buttons together)
    • In Recovery mode, create Nandroid backup of present ROM (to do so, select Backup and Restore > Backup) and return to main Recovery menu after process is completed
    • Perform full data wipe by selecting Wipe Data/Factory Reset > Yes and return to main Recovery menu after process is completed
    • Select Install Zip from SD Card using Power button and then Choose Zip from SD Card
    • Browse to Jelly Bean ROM saved on device, select and confirm installation
    • After ROM is installed, repeat procedure to flash Google apps package
    • After installation, return to main Recovery menu and select Reboot System Now
        • Note: To restore previous ROM boot into Recovery, choose Backup and Restore and select desired ROM from list  

CM10.1 custom firmware, based on Android 4.2.1, is now installed and running on the Samsung Galaxy S (I9000). Browse to Settings > About Phone to verify firmware version on device.     

[SourceXDA Developers]