A few months ago I installed ubuntu alongside windows and everything was working fine. However I only gave the ubuntu partition ~7GB of memory, thinking I wouldn't use it as much. Long story short, turns out I needed a lot more memory for it, so I completely wiped my hard drive, merged all the various partitions I had and started from scratch. I first installed windows. While doing that, from the windows installer I created 3 partitions. 1 - Windows (~300GB), 2 - Various stuff (~50GB), 3 - Ubuntu (~350GB). I installed windows on the first partition with no problem whatsoever. But when I tried to install ubuntu on partition 3, it popped an error saying:
"/dev/sda contains GPT signatures indicating that it has a GT table. However it does not have a valid fake msdos partitiontable as it should. Perhaps it was corupted possibly by a program that doesn't understand GPT partition tables or perhaps you deleted the GPT table and are now using an msdos partition table.Is this a GPT partition table?"
I am pretty new to the world of "partitioning" so I have absolutely no idea what any of that means. So, any kind of help would be immensely appreciated. But please, PLEASE, remember that I'm a newbie to all that stuff, so I probably won't understand very technical solutions. If you kept it simple, you'd have my never ending gratitude. Thank you in advance.
EDIT: I forgot to mention something I think is rather important. When I try to create a partition using the ubuntu installer, it says that I have ~685GB of unallocated space. (I have a 700GB hard drive, so it thinks it's completely empty). I think it doesn't recognize any of my current partitions.