Before Starting please remove your launch.ini off of your console.

Extract the .RAR for Nand Flasher.
Make sure your USB Drive is FAT32.
Place the Simple 360 Nand Flasher, on the root of the USB.

Go to XeX Menu, and load the Default.xex for Nand Flasher.
You'll be presented with this screen:
[ Register or Signin to view external links. ]

Hit X to Dump the Entire Nand.

When it finishes, you'll be presented with this:
[ Register or Signin to view external links. ]

Hit any button on your controller, and when you're back at the Dash, take out the USB Drive.

You'll see 4 Files now in the Nand Flasher Folder:
[ Register or Signin to view external links. ]

Backup the flashdmp.bin in case you need to flash back!

Download and Extract XeBuild 17544.
Open the file named XeBuild GUI 2.0.

On the top of XeBuild, to the right of Source File - Hit Open and select the file "flashdmp.bin".
[ Register or Signin to view external links. ]

If you have a 4GB Corona (48mb Nand) it'll give you this error:
[ Register or Signin to view external links. ]
Hit YES.

A little bit under that same spot, you'll see Keys.
Next to the text box of CPUKey, hit the button "Get CPUKey from Keys.txt".
Select the file "cpukey.txt" that Simple 360 Nand Flasher made:
[ Register or Signin to view external links. ]

Double Check the Build Type!!
If you have a Slim Trinity or Corona, it'll be Freeboot (RGH 2.0).
If you have a Phat, you need to know whether it's RGH 1 or 2.
If you're unsure, Dashlaunch will tell you in the bottom right.
Always select Freeboot, not ECC.
[ Register or Signin to view external links. ]

The last thing needed to do, is to select the 17526 Kernel.
It should be auto selected, but if it's not:
[ Register or Signin to view external links. ]

Please make sure all boxes on the bottom are Checked:
[ Register or Signin to view external links. ]

If you're on a 4GB Corona, this step is very important.
You NEED to enable 'Open Parameter/Argument Editor':
[ Register or Signin to view external links. ]

Once you have completed those things, on the bottom of XeBuild hit the button Labeled:
"Generate hacked image".

If you get an error saying it cannot find files, hit Yes.
After it 100% Downloads, hit Generate Hacked image again.

If you get an error message that says this:
[ Register or Signin to view external links. ]

Then double check your build type again.
If you are 100% positive that you selected the correct one, then hit No.
Then it'll bring up another Popup asking if you're sure you wanna use it, hit Yes.

If you have a 4GB Corona, you'll be presented with the same error you had earlier.
The only difference is, you'll get a Popup that looks like this:
[ Register or Signin to view external links. ]

All you're going to do, is add 4g to the end of Corona like this:
[ Register or Signin to view external links. ]
Then, just hit Save the New Parameter.

In the Right window of XeBuild, if all is successful you'll see a Log that looks like this:
[ Register or Signin to view external links. ]

Go to the Output path, where XeBuild saved the file, and you'll see the file "updflash.bin".

Drag that updflash.bin into the Simple 360 NAND Flasher folder on your USB.
[ Register or Signin to view external links. ]

Once moved, take the USB, and put it into the Console.

Go to Xex Menu and start the Default.xex for Simple 360 NAND Flasher.

Once it is loaded, hit A to Write Your Nand.
Then hit Start to confirm the Write to your Nand.

When it's completed, you'll see:
Rebooting in 5....4....3....2....1.... and then the console will automatically reboot.

When the console reboots, if you go to Settings and Console Info, you'll see you're officially updated, and on 17526.
Congratulations on Successfully updating your console.

You'll more than likely need to do an Avatar Update.