Try this guide:  http://www.theandroidsoul.com/how-to-root-xwjvh-android-2-3-3-rom-for-galaxy-s-i9000/

See the following page for downloading the required files:  http://www.theandroidsoul.com/how-to-root-xwjvh-android-2-3-3-rom-for-galaxy-s-i9000/

1. Install Samsung Kies but dont keep it running while flashing as it will interfere with the process. Required only for the drivers.
2. Download CF-Root kernel. File name – CF-Root-XW_NEE_JVH-v3.2-CWM3RFS.zip. Unzip the above file. You will get the .tar file – “CF-Root-XW_NEE_JVH-v3.2-CWM3RFS.tar”.
3. Download Odin. File name – Odin3 v1.7. Extract the zip file to get Odin3 1.7.exe. Run Odin by double clicking on it.
4. Switch Off your phone. Wait for vibration to confirm complete switch off. Boot your phone in Download Mode — Press and hold “VolumeDOWN + HOME key + POWER button” together.
5. Connect your phone to PC now. You’ll notice “Added! !” message in the message box. On Odin, click the “PDA” box and select the .tar file you got in step 2 — CF-Root-XW_NEE_JVH-v3.2-CWM3RFS.tar
6. Do NOT select any “.pit” file in the “PIT” box, and make sure “Repartition” button is NOT checked. Leave the “Auto Reboot” and “F. Reset Time” buttons checked. Click the Start button on Odin to begin installing the CF Root kernel. After the CF Root is installed, phone will restart. Your phone is rooted now. Note that surperuser app is there.