[AT&T Samsung Galaxy S II SGH-I777] bowenac:
Ok I decided to post this because out of all of the phones I have rooted and flashed this had to be the most confusing... to many different options, and scattered all over the place.

I know some people are against making things easy for people but thats just not me and doesn't make any sense at all.

So here was my working method.

USE AT YOUR OWN RISK

ROOT download I777UCKH7 OCD Root No BL.7z from here credit goes to Entropy512

How to Use:

Download the 7 zip package. Extract the contents of the zip file to a directory on your hard disk drive.

Start the Odin3 One-Click Downloader program by double clicking on "I777UCKH7 OCD No BL.exe" or "I777UCKH7 OCD Root No BL.exe".

Now Enter Download Mode:

With the phone powered off, plug in the usb cable while holding the vol up + vol down buttons (but not the power button).

When the warning screen appears, press Volume up to continue into download mode.

In Odin, the small edit box in the upper left corner will turn yellow, and say something like [0:COM8]. The number could be different.

Click Start. Watch the progress bar advance in green while the message box in the lower area describes the steps. When the flash is finished, the top left larger edit box will turn green and say PASS! and your phone will automatically reboot.

Unplug the usb cable from you phone after it boots up. Success.

OPTIONAL Unlock If you would like to unlock your phone for other gsm carriers. I have tested this on T-Mobile and it works. Once you are rooted and verified you have super user. Make sure you have busybox if not download it from the market. Also make sure you have a micro sd card installed.

Go to market and search for "Galaxy S Unlock", the author is "Helroz".

Run the app from step 2. Go to "Unlock SGSII" tab on the top of the screen.

Tap on the first item:"Step 1 Backup files...."

Tap on the second item:"Step 2 Change lock-bytes", and wait until your phone restarts.

Bingo, your phone is sim unlocked after the reboot.

Flash Clockwork

NOTE THIS METHOD WILL VOID YOUR WARRANTY BY INCREASING THE PHONES FLASH COUNTER HOWEVER YOU CAN RESET IT USING THE NEXT STEP

You will need to download yet a different odin you can get that here

Download the attached Siyah rom since it is the only tar file I could find and odin only accepts tar files. This will flash a new kernal and clockworkmod. I attached this because it seems the link is dead.

How to use:

Start Odin

Now Enter Download Mode:

With the phone powered off, plug in the usb cable while holding the vol up + vol down buttons (but not the power button).

When the warning screen appears, press Volume up to continue into download mode.

In Odin, the small edit box in the upper left corner will turn yellow, and say something like [0:COM8]. The number could be different.

Click the PDA button and browse to the Siyah Rom

Click Start. Watch the progress bar advance in green while the message box in the lower area describes the steps. When the flash is finished, the top left larger edit box will turn green and say PASS! and your phone will automatically reboot.

Unplug the usb cable from you phone after it boots up. Success.

Reset Flash Counter and remove warning triangle

I read that you need to be on an ICS rom for this to work. After flashing CWM I flashed F1 rom.

Download this apk TriangleAway v1.70 you can get that here

I have tested this and it does work, when I tested this my flash counter was at 3 now it shows Custom Binary Download: NO... also no more gti9100 with yellow triangle.

You should now be able to boot into clockworkmod recovery and be able to flash zip roms from your phone like normal "or like any other phone you have had that has had cwm installed".

DO ANY OF THIS AT YOUR OWN RISK

I DON'T TAKE CREDIT FOR ANY OF THIS... JUST WANTED TO GET THAT OUT THERE This is just for anyone else who may be confused with the amount of links and scattered content just to root and get cwm installed.