I'm a newbie to GParted and Ubuntu in general. Basically, my main partition (boot) was mounted and I couldn't edit it in any way so I got very frustrated and, without really thinking, tried to forcibly unmount it. Now my PC won't boot up and I really have no idea what to do
You need a LiveCD, which is just a bootable Linux CD. Once you boot into that, mount the hard drive somewhere, then view the logs in the mounted folder.
Load gparted from the LiveCD to find the device name of the boot partition. Let's say it's /dev/sda1.
Then open a console, and create a folder for mounting:
Then mount the boot partition:
Change to the log folder:
Display the logs in date order:
Now check any recently-modified log, such as syslog: