QUOTE(Shizuru @ May 8 2012, 11:17 PM)
which method did you use for root?
what file did you download?
1. Power your device off (shutdown)
2. Boot into Download-Mode using Volume Down + Home + Power
3. Hit Volume Up to accept the warning
4. Start Odin on PC
5. Click PDA box and choose "GT-I9100G_XX_ClockworkMod-Recovery_X.X.X.X.tar" that you downloaded (Note this is .tar file) (DO NOT tick repartition)
6. Connect your Phone to PC
7. If odin detect your phone the first box will turn yellow
8. Click start
9. Once successful the first box will turn green
10. Device will auto reboot.
11. After reboot you can easily root your device using SuperOneClick. This will install superuser and busybox for u.
Edit
Note:
1. Make sure kies is installed for the correct drivers to allow odin to detect your phone
2. BUT make sure kies is not running in the background or odin will not work. Open up your pc task manager and kill anything with the word kies on it.
3. Some people prefer to disable antivirus also.
4. Never ever disconnect usb cable while flashing.
http://forum.xda-developers.com/showthread.php?t=1631934