Even though Samsung denied an update for the Galaxy S I but still the developers at XDA worked hard to port ICS to this device. Today I would like to help you install CyanogenMod 9.1, one of the most stable versions of ICS, on GalaxyS I.
Please note that this is risky and you would be doing it at your own risk. Noone, including me would or can be held responsible for any screw-up that you end up with. Also, please read the article very carefully and follow as instructed to avoid any complications. Best of luck.
CyanogenMod is based on the Android Open Source Project with extra contributions from many people within the Android community. It can be used without any need to have any Google application installed.
We need 2 files, one is the bare ROM which is the main file and the second is Google Apps which is optional, needed only if you want Google apps. However, I would personally recommend its installation.
Download the file, extract it and copy the two files (ROM & GAPPS) on your internal SD card.
Download the above two file and save them on your internal SD card.
Back-up: It is very important that you completely back-up your phone before you start your act on anything in this article. This will save your data and help you restore your stuff quickly. You cab use Titanuim Back-up or any other back-ups you have.
(i) Your phone should be rooted. If you are not sure, see if your apps lists has SU installed and if yes, click to see if it has root access. However, if you are not rooted or su does not have root access, visit my this article on how to root your phone first [https://www.fixmystuff.in/FMS_Forum...i9000-rooting-gt-i9000-2-3-3-india-ddjv9.47/].
(ii) ClockworkMod Recovery should be installed. If you are not sure if it is installed, then download ROM Manager from the market and install. Once installed, open ROM Manager, it will ask for root access, grant it and click on the 1st option "Flash ClockworkMod Recovery". On the Phone Model confirmation, select "Samsung GalaxyS i9000". It will download and install ClockworkMod Recovery.
(1) Reboot into Recovery: There are 2 ways to boot into recover, you can use the 3 button combo [Volume Up + Home + Power] or you can open ROM Manager and select the 2nd Option "Reboot into Recovery".
(2) wipe data/factory reset: This would be the 3rd option. Scroll to this option using your volume up/down button and select using the Home button. It will take you to a new screen, select "Yes -- delete all user data"
(3) wipe cache partition: This would be the 4th option. Scroll to this option using your volume up/down button and select using the Home button. It will take you to a new screen, select "Yes - Wipe Cache"
(4) wipe Dalvik Cache: Scroll to "advanced", this would be the last option and select it. It will take you to a new screen, select "Wipe Dalvik Cache". This will take you to another screen, select "Yes - Wipe Delvik Cache". Then select the last option "+++++Go Back+++++" which will take you to the home screen.
(5) Installing new ROM: Select "install zip from sdcard". It will take you to a new screen, select "choose zip from sdcard", in the next screen select 1st file you downloaded, i.e., "cm-9.0.0-galaxysmtd.zip". In the next screen select "Yes - Install cm-9.0.0-galaxysmtd.zip". This will take sometime, so relax. If this is successfully done it will take you to the home option page. If it enters into a boot loop, repeat the steps from (1) again.
(6) Installing Google Apps: Select "install zip from sdcard". It will take you to a new screen, select "choose zip from sdcard", in the next screen select 2nd file you downloaded, i.e., "gapps-ics-20120429-signed.zip". In the next screen select "Yes - Install gapps-ics-20120429-signed.zip". This will again take sometime, so relax. Once done it will take you to the home option page.
(7) Select "reboot system now" which should be the 1st option.
ICS has been installed on your phone. Enjoy.
If incase, you have screwed up anywhere and intend to revert to original ROM, read my this article [https://www.fixmystuff.in/FMS_Forum/threads/samsung-galaxy-s-gt-i9000-flashing-to-original-rom.46/]
Thanks to the XDA Developers for the attachments and all the knowledge.