Newbie stuck & now lost

Hi,
I mounted an iso file as it would not load correctly otherwise.
I have been using the file no problems when mounted in DT lite.

A couple of days i have noticed that the file would like to try and start itself when the pc starts.
Being a newbie i have unmounted "i think" the file,as now the software tells me to insert the disc.
Is there a way i can mount it again as i cant now find the iso file that it was working from.
Is there some kind of directory to show previously mounted files ?
Thanks