Howdy! Recently picked up this board and I am trying to install windows 7 onto my 3 TB drive. Keeps saying the drive is invalid due to being formatted in GPT. Deleting the partition and repartitioning during the install only allows me to make a 756GB partition instead of the full 3 TB.

I found out I need to boot it up into UEFI mode. I'm having a heck of a time trying to figure out how to do this.

So far I tried a few things.

-kept the original bios ver (0202) on bios one and switched over to bios two. I upgraded that bios to the latest ver (3603).
-put my 3 TB drive on the intel sata III 6gb slot (the red ones touching the grey ones).
-set the option to boot into efi compatible bios instead of legacy
-set to boot from dvdrom first

When ever I load windows 7 install from the dvdrom, I get the same GPT error. I also don't have a usb drive over 2gb to put a windows install on that.

Anyone have some tips? Ty for your time!

2600k sandybridge
Maximus IV Extreme-z
3 TB HDD

-----------------------Last Edit------------------------------------------
So 2 days after I did all this, my OS drive (3 TB drive) goes nuts and crashes. Couldn't save the install. Didn't have access to the original 8gb USB to reinstall so I decided to install the OS on the SATA and call it a day. There were problems.
--Window's install didn't want to touch my SSD while my HDD was still installed. Had to disconnect the HDDs till after the OS install.
--Had to disable the Acceleration via the Ctrl-i menu when the Sata config is set for Raid.
a. Ctrl-i unaccelerate the HDD
b. Then set the cache drive to non-raid status
c. Set the config for Sata drives to AHCI
d. Disconnect all drives except the SSD to install windows.

-----------------------Big edit to explain full process------------------------

Hope this helps someone. Here is what I had to do to finally get windows installed on a 3 tb drive and have my SSD accelerate the OS drive using Intels Rapid Storage Technology (RST).

----Flashed my 2nd bios to the latest ver (3603). HEADS UP - I started with bios 203 so I had to FIRST flash to 902 because 3603 just wouldn't get recognized. Then I could flash to 3603.
**HEADS UP --- after 3603 was flashed, I had to remember to turn off the -pause for f12 on error so I could try to boot CD or USB. Also I set the bios boot to EFI supported bios (as opposed to legacy). It's in the boot options in the bios. Save and exit.

----Used rufus to create a UEFI boot drive using a win 7 64 ISO (http://www.howtogeek.com/forum/topic/how-to-do-a-clean-install-of-windows-7-8). You could also use a windows 7 DVD install, but I couldn't find one that had that would boot into UEFI mode. I used an 8 GB flash, but my iso install was under 4 GB.

----Made sure my HDD that was going to be my boot drive was in the INTEL sata ports.
**HEADS UP --- If using the 6gb ones they are the red ones NEXT to the grey ones. The other red ones are marvell ports (cant be used for RST). I put my SSD in the other intel sata 6gb port. The grey sata ports are all intel 3 gbs.

----Put the usb in the ROG Connect USB slot. Quite important. Before I did that I would get constant "driver not found" errors during the install. Disconnected all my drives expect the OS drive during the OS install. No particular reason. I just didn't want to confuse myself while picking which drive to install the OS.

----With USB in ROG Connect Slot, boot into the bios and check your boot options. Set your first boot to UEFI "YOUR USB NAME". Whatever you called it. Mine was called UEFI General USB. If you don't see a UEFI USB or DVD option, your USB boot drive (or dvd) was not setup correctly. Redo it using rufus.

----At this time also set your Sata configuration to RAID (options are IDE, AHCI, RAID). Its the 3rd tab? Or 2nd. Just go through the tabs to find the Sata Config. RAID IS KEY here before the install.
**HEADS UP --- this is NOT the Marvell or Jmicron sata slots. It's the primary Sata config. SAVE AND EXIT.

----Hopefully now you are seeing a windows install prompt. Hit install, and it should ask you which partition to use. For me, the 3 tb drive was the only one there and it STILL only showed itself as 746gb. Didn't matter. I just selected the drive and Installed. Later, once you install the chipset drivers you can extend the partition and add the rest using diskmgmt.msc. Refer to bruces comment about diskpart before you select the drive (http://www.makeuseof.com/answers/get-3-terabyte-hard-drive-display-entire-storage-capacity-windows-8...). This should set things in GPT mode for the drive, but I STILL couldn't get it to show more than 746 gb. Didn't matter, after I extended the partition to add the rest.
**HEADS UP -- I had to put my mouse in the USB2 slots to even be used during this time.

----Windows hopefully installed, things going well. FIRST thing to do, install current chipset drivers. I used Intel_Chipset_V9201030_XPVistaWin7.zip and then after the reset, IntelMEI_V7001144_Windows.zip (both extracted of course). Get the most current ones on the Asus ROG site.

----Now you can install the rest of the Asus ROG drivers if you want. You also need to download the most recent intel RST drivers. I used (https://downloadcenter.intel.com/product/55005/Intel-Rapid-Storage-Technology-Intel-RST-) 13.6. Before you can install RST you need the Netframework 3.5 (or latest) install from Microsoft. I just used the Windows Update to install those first.
**HEADS UP --- I had a heck of time installing the 255 updates from Windows update. Super slow, and half failed. Install them in batches of 5-8 if you are having issues. Installing all these updates might not be necessary to get the RST up and running. I can't tell for sure since I did at least half of them (7 hours of downloading and installing).

----With Net framework installed, install the RST driver. With the RST driver installed, shutdown the pc and you can connect the SSD into the other INTEL sata port (NOT the marvell ones..which are the last 2 red ones). If the SSD is formatted or partitioned, delete all the SSD volumes. You can use diskmgmt.msc to do this. It should be its full unallocated space.

----Now, open RST (in the notifications is should be running...right click and open). It should have an accelerate option waiting for you in the performance tab AND the Manage tab. Anywhere it says accelerate, click on it. There it will give you the option to use the SSD (UP TO 64 gb) to accelerate your OS drive. I used the maximize option.
**HEADS UP --- At first RST just would give me the option to accelerate anything. Finally I found brads answer (http://superuser.com/questions/546601/no-accelerate-button-tab-on-intel-rapid-storage-window). It was because I had the SSD formatted and allocated. Make sure it has no volume.

----If you had an SSD larger than 64 GBs, you can now allocate the rest of the drive to its own partition using diskmgmt.msc. Reset the PC a few times or more to get it to start cacheing your OS files. You will see faster boot ups.
BAM This was a hellish and convoluted method that had me yelling a bit. Hopefully it helps a bit. This was all so I could install MOST things on my huge 3 TB drive and still benefit from the SSD speed. Apparently games don't benefit too much from this from what I read. I'll be testing some more and give you an update on whether its worth it.