Basically it is just copies of things that you have seen or heard
while
opening your mail.
It is not the original files, so when you delete mails...all the
contents
that made up the stationery are still in the RunTime folders.
 
No you will not lose anything that is on your incredimail, for
example
deleting the files in your sounds folder will not effect the sounds
you have
saved in Incredimail.
 
Fear not grasshopper! Smart of you to ask!