If I understand correctly, you want to mount r/w the partition where your iso image is.

When you boot from a iso image on disk (as in your poor man's install), the partition where the iso is will be mounted as a cdrom loop device in read-only mode. For example, if the iso file was on hdd1, then mount will read "hdd1 on cdrom2.loop type ext3 (ro)".

To make hdd1 writable, issue the following mount command:

mount /dev/hdd1 /cdrom2.loop -o remount

Regards.