Mid 2011 iMac Bootcamp Issues?

So I decided to bootcamp using a Windows 8 ISO and a USB drive.
I followed all the steps in Boot Camp Assistant and then I restarted.
When I booted up I held down option and selected my USB drive to boot from which worked fine until I ran into an issue where I was told to select my drive (in windows)
I selected my drive but it said my drive must be GPT not MBR. I didn't know what to do for quite some time and decided to go look it up on my Mac OS by restarting, holding down option and selecting my OSX drive. I then found the solution here: http://www.youtube.com/watch?v=g2iFj56NDg8 (watch for better understanding, please)
I restarted my computer and loaded up into my USB like I did before and did what he did in that video but I accidentally changed my OSX normal drive to GPT as well, but I did not think it was an issue, so I continued on without trying to change it.

After I did that I entered in my activation code, which worked previously, and it didn't seem to work (which was my initial problem which lead to this one.)I tried to re-enter my code many, many times and I eventually gave up and decided to go back to my regular OSX (mac). I restarted and held down the option key and neither my regular OSX drive, nor my USB drive were in the boot menu.

I then tried booting into the recovery mode "CMD+R" and repairing my disk but I get the error: "Partition map check failed because no slices were found" for both my normal OSX drive and my USB drive.

The only option I can really think of is just restoring my computer but I have many MANY important files on there and I do not wish to lose them.
Any help would be great. Thanks.

Well tell us about your Mac. If it came with an optical drive it will not install from anything else but a DVD. Sounds like you have formtted the Mac OS X partition NTFS - very easy to do.

And it helps if you provide al computer and operating system details.

You obviously ignored the Boot Camp instructions. As Harry stated, since your iMac has an optical drive you should be installing using a Windows 8 DVD. The BC instructions also caution about making a backup before attempting to install Windows via BC. Also, your Macintosh HD will not boot if you changed it to GPT as it has to be EFI. I really don't know how you're going to recover your data. I don't believe an OS X data recovery program can read a GPT partition in order to recover files. Without a backup you may be out of luck.

Is there any way I can boot up as a GPT?

Is there any way I can boot up as a GPT?

Click to expand...

You can't boot a Mac that way. Macs boot from EFI. You may be able to remove the hard drive from the iMac (not an easy job) and place it in a SATA carrier and possibly read the data off it from another Mac. But no guarantees. Your iMac if I remember correctly uses a Seagate 500 GB hard drive unless you opted for the 1 TB drive when you purchased it.