I've been experimenting with GPT partitioning for a few weeks now on a new hard drive that I bought purely for this purpose. The main reason for this was to see if creating a octo-boot (or larger) system is possible with a GPT scheme. I created a GPT disk through Gparted, created a hybrid MBR with Gdisk, partitioned according to how I wanted my system to look with a large multi boot system, and started installing. Good news, bad news. The good news is, it worked perfectly, and aside from minor problems with the grub screen bugging out a few times, the system is happily running. The bad news is, it worked perfectly and now refuses to boot to my other hard drive which has MBR partitioning on it. The problem began when I decided to get my boot screen looking pretty again (rather than having 64+ entries in it). I downloaded Boot-repair, ran it, and poof, boot screen was nice looking again... but, it brought about this.
I forgot to read a little more ahead on the differences between the MBR and GPT in how they determine where to search for a boot record. Now, when swapping out from my GPT partitioned hard drive to my MBR hard drive with Ubuntu and Windows, I am unable to boot, and am immediately put into the grub rescue console. At the moment, my live usb is at home, which I suppose I could use to reinstall everything, except that requires gettinng onto my other hard drive and reinstalling the systems. Using the Grub rescue commands is getting me nowhere right now. All that is returned from every partition that I try access is "No known filesystem detected."
Things I have tried:
http://ubuntuforums.org/showthread.php?t=1599293 - some of the things here (requires a cd though, so not too much good)
The question is, is there anything that I can do at this moment without my live usb to fix this and be able to get into my other hard drive to use windows? I assume that completely reformatting everything during an install would rewrite the GPT partitioning scheme back to a MBR, but... this took me a few weeks to learn everything and finally get running. I'd prefer not to do that.