Embedded SO are as the name suggests are a copy stored within the doc, they are only temporarily opened and saved to the unique temp folder path when edited in that session. Quitting and restarting Photoshop and editing the SO again would reveal a new path that would ...
The only way to fix a drive that's full is to delete files from it to make more room (or get a bigger drive). In order to know which files are taking up space and which are safe to delete, you can run a disk space analysis tool. You can also run Windows Disk Cleanup tool to ...