Can't Copy Windows 7 Install Disk

[i_am_jim]

I'm doing system rework and need the Windows 7 installation disk a lot to go into the repair console.  I dropped it a couple of times and decided I need a backup copy in case it gets damaged.  But, when I try to make a copy ImgBurn reports the problem shown in the screen shot below.  Anybody know what's wrong?

[LIGHTNING UK!]

Burn it to a double layer disc.