Changing permissions on my cloned drive

Hi,

I am looking for help in order to reset permissions on clone image that I created.

My internal hard disk has kind of crashed and the attempts to recover disk had failed, I followed dsstore instructions but was unable to restore the disk or create an image using disk utility.

So I made a bootable external hard drive and used Data Rescue 3 to clone all the data from the internal drive, as it was unmountable. The application created a .dmg image which I can mount to extract data.

I wanted to ask is it possible to change the permissions on this image to delete files, I have read through the forums and tried a couple to things but they don't work. The GetInfo permission section is greyed out and Disk Utility Repair disk permissions is also greyed out.

Would appreciate any help