- First go to Settings -> Applications and put check on "Unknown Sources". This will allow you to use cracked apps.
- Second step is to download the z4root from the link above.
- Locate the z4root using file manager (download the astro file manager it's best and free)
- After installation lunch the apk and select the "Root" option. And the you're done.
I repeat this has worked perfectly on my GalaxyS!!