I recently lost some software which at the time I did not think I needed but then found out that I needed it so I had to piece it together from an old backup.

I know many of you back up software to a rewriteable DVD but can you make a copy of it to an external HDD and then when you need it you can write that copy to an external DVD?

Can you do that? Is that recommended? I am in OS X. Thanks

Also if you make a copy to an external HDD can you use that to install from? I think I tried this once on OS X but it would not because OS X needs to be installed from a DVD or CD player. Is that true of all software?