I couldn't find any threads for moving from regular Win8 to Win8 Pro on the same hard drive so I wanted to save someone else four+ hours. I'm used to wanting to pull my hair out when it's time to install drivers, not getting the OS on the system. Strangely, the driver part went smoothly.


Important Note
Don't bother with a CD/DVD. If you don't have a USB drive, go buy one, right now. I have a pile of coasters because of UEFI and I never did get around this problem*.

*There are two boot images on the ISO: etfsboot.com and bootx64.efi. etfsboot.com does not work. If you have to use a DVD, I would try bootx64.efi


What this guide is
This guide explains how to do a fresh install of Windows 8 Pro over your pre-installed Window 8 OS hard drive. That means this is a different serial key than the one in your BIOS and you'll be reformatting the hard drive that has your current OS on it. This guide does not remove the Asus recovery partition.


Unlock the BIOS
The following is preventing you from installing another OS. You need to
- disable fast boot [eightforums.com] in Win8
- testdisable Secure Boot Control from inside BIOS (F2)
- enable Launch CSM from inside BIOS (F2)


Download Your ISO File (CD key required to download)
You will need to add files to the ISO in the next step so you just can't use your retail/OEM disc. You can either download Pro from Microsoft (link below) or rip an ISO of your Win8 Pro CD with your favorite ISO ripper. Downloading took about 10 minutes, but you need to be on a Windows machine and whatever architecture that Windows machine is using is the architecture your ISO will be. So if you want a x64 ISO you need to download from an x64 Windows machine. I've read that a virtual machine will work but can't confirm.

Upgrade to Windows 8 with only a product key [microsoft.com]

Follow the instructions at EightForums for using the download software if you need to. Save the ISO file to your desktop


Preparing Your ISO
Create a file called PID.txt and paste the following into it.

[PID]
Value=XXXXX-XXXXX-XXXXX-XXXXX-XXXXX 

Replace the Xs with your Win8 Pro key (dashes required). We're doing this because if we don't, your install will try to use the old Win8 key in your BIOS.

Since we're installing Win8 Pro, we do not need to make the ei.cfg file that's in the sticky.

Use 7-Zip, WinRAR or WinZip to extract your Win8 Pro ISO to a folder, then copy your PID.txt. into the "sources" folder (C:\...Desktop\Windows_8_Pro_64-bit\sources).


Putting Files on USB
- Format your USB drive to FAT32 (NTFS does not work with UEFI)
- Copy the /contents/ of your ISO folder onto your USB drive (don't include the main folder)

The above is all you need to do to make your USB bootable. This is why USB is the way to go for this--your machine picks which boot file to use.


Booting from USB
Restart the computer and hold down ESC to get the boot manager. Choose your USB drive (the drive name will start with UEFI). FYI your optical drive will start with the manufacturer followed by some numbers (i.e. P2: ASUS 12345-12345-X).

If you get an error trying to boot from the optical drive, you burned yourself a coaster. Take a drink.


Windows 8 Install Wizard
Agree to sell your soul to MSFT and choose Custom: Install Windows only. I had four partitions with my fourth being the primary and my first being the Asus recovery. Click on your primary partition, choose Drive Options. Click Format. Tell it okay when it warns you that formatting will erase stuff. After it's done, choose Next. In the G55, install took about 5 minutes so don't go anywhere.


Windows 8 Install Wizard - GPT Partition Style Error
If you click on your primary partition and get this error "Windows can not be installed on this disk. The selected disk is of the GPT partition style." it's because when you burned your bootable DVD you didn't tell it to use UEFI. Try telling it to use bootx64.efi instead of etfsboot.com. If that doesn't work, get a USB drive.

And you're done. Time to customize your OS install and insert the Utility and Driver CD your laptop came with.


Additional Threads
[GUIDE] G55/G75 Upgrade Notes
Clean Windows 8 install on GPT SSD drive (G75VX)