[Galaxy S I9000 Q&A, Help & Troubleshooting] scubadude:
CF-Root info here: http://xdaforums.com/showthread.php?t=788108

From thread:

Instructions (long)

- Follow these instructions to the letter. Do not touch any buttons or checkboxes that are not listed below to touch!

- Unzip the attached CF-Root-xxx-vX.X.zip

- (USB) Disconnect your phone from your computer

- Start ODIN

- Click the PDA button, and select CF-Root-xxx-vX.X.tar

- Put your phone in download mode

- (USB) Connect the phone to your computer

- Make sure repartition is NOT checked

- Click the START button

- Wait for the phone to reboot

- Done (if it took you more than 30 seconds, you need practise!)

Help! I don't know which file to pick! The filenames confuse me!

First thing: don't panic! It's all rather easy, and you won't easily do something bad! I am personally attentive to use the exact same version as the ROM I am running, but it's not that important.

First, go to Settings -> About phone -> Build number. It should say something like FROYO.xxJPy. It's primarily the JPy that we are interested in. Try to match that with a download link available in this (and the next few) posts. Some of the downloads dont just have JPy file name format, but are called xx_xxx_JPy.

Find the one that is closest to yours, if yours is not present, and flash that one.

If you are just installing CF-Root to flash a custom ROM like Darky, make sure you have ROM Manager already installed, ClockworkMod flashed, then simply install the latest CF-Root, reboot once normally, then reboot in recovery and run the Darky update.zip. In this case it does NOT need to be a near match at all!

Before you start it is a good idea to download your stock rom or another one for your phone from here.

http://www.sammobile.com/firmware/?page=3&t=1&o=1&m=GT-I9000&r=-1#modelsa

Then where it says region click your country.

I recommend getting everything you need before you start. So make sure you Odin, a 512 pit file & your stock rom with the PDA, Phone & CSC files. There are plenty instructions for getting back to stock if you search.

Next get the ROM you want & the kernel you want.

Now that you have everything you are ready to go.

My process is as follows.

1. Remove SD Card, some say to remove sim but I have never done this.

2. Turn on phone & turn on USB debugging.

3. Connect phone to usb & copy everything on my internal sd card onto my pc. (I have a samsung folder & create a folder with the date and put everything in there - just in case)

4. (USB) Disconnect your phone from your computer

5. shut down phone.

6. Follow cf-root thread instructions.

7. Unzip the attached CF-Root-xxx-vX.X.zip

8. Start ODIN

9. Click the PDA button, and select CF-Root-xxx-vX.X.tar

10. Put your phone in download mode (power on, volume down, home button)

11. (USB) Connect the phone to your computer

12. Make sure repartition is NOT checked

13. Click the START button

14. Wait for the phone to reboot

15. Done (if it took you more than 30 seconds, you need practise!)

Now you have root & cf-root. Restart phone. Next step is generally as follows.

1. Start phone.

2. Connect phone to pc.

3. copy files you wish to flash onto root of internal sd card. in my case team icssgs 4.2 & semaphore 0.9.1

4. (USB) Disconnect your phone from your computer

5. restart phone into recovery.

NB. Make sure to do a backup at this point and ensure you have a copy of your efs folder somewhere!!! - if for some reason your IMEI number is corrupted you will need this

6. factory reset & clear cache

7. advanced button -> clear dalvik cache.

8. back & choose install zip from sd card

9. choose zip from sd card.

10 .select the zip file (in my case team icssgs 4.2)

11. Choose yes- install... zip name

12. repeat steps 8-11 and select semaphore kernel.

13. factory reset & clear cache

14. advanced button -> clear dalvik cache.

15. reboot phone. Reboot can sometime take a while. sometimes you may need to do this twice.

Semaphore: http://xdaforums.com/showthread.php?t=1468795

Team ICSSGS: http://xdaforums.com/showthread.php?t=1398223

If no luck then reinstall stock rom using odin making sure to use all three files & pit file with repartition checked.

Please note I am still fairly new at this so it may not be perfect & you should always rather follow instructions from the thread of the ROM you wish to flash

Hopefully that's it. Don't think I left anything out.