Never too late to make the move to open source and this great operating system. All it takes is a bit of time and effort to learn the tools.
In your case, the disk in all likely hood became "read only" because ubuntu detected file system errors and locked it to prevent any further corruption,
Let's look at the disk and see how it is formatted and then see what we might be able to do from ubuntu's perspective on that disk.
Boot up from a liveCD, so no disks are mounted;
Plug in the disk and let's see/
When we know more we may be able to run a file system check/repair, also we will want to know that the disk is not filled to capacity(when we know the disk identifier).
sudo fdisk -lu
sudo parted -l
sudo parted /dev/sda unit s print
but, one thing at a time and we will get there