I just tried the Go>/Volumes and got an alias to my hard disk. It is a bit pointless really because Finder will show these in the sidebar, depending on your preferences. Here are mine for your information.
Regarding the disk usage, is the first screenshot the new account and the lower one the other computer?
It looks like you have more than twice the number of photos now, would that be right? Are there several libraries? If you open iPhoto holding the Option key, it will show you a list of available libraries. iPhoto Library Manager has a merge function for this, amongst other things.