I download .iso's all the time, and wanted to be able to mount iso's for winblows games on wine. What this does is map your iso to a filesystem directory. Here is what I did, and here is what you can do as well.
First grab fuseiso
sudo apt-get install fuseiso
If you are in firefox and have apt-url installed click here to install with one click!
Then lets add ourselves to the fuse usergroup
sudo adduser myusename fuse
If you were not in the fuse group you will need to log off, then back in right now.
Now lets create ourselves a fuseiso folder to mount our iso
sudo mkdir /media/fuseiso
Now we just grabbed an iso off the net, so lets mount it!
sudo fuseiso myisofile.iso /media/fuseiso
Ok now the iso is mounted and we can use it like its a cd/dvd
Nautilus/cd your way to /media/fuseiso and the files from the iso will be mounted readonly.
More information on fuseiso can be found here