I think this only applies to a OEM disk provided by a computer manufacturer (specially modified\branded by the manufacturer) and intended to perform an unattended install on the machine it came with.
There is an OEM disk offered by MS at a discount.
It is intended to be used by a manufacturer to install Win 7 on a newly built machine.
It does not install unattended. It will ask for the product key at the appropriate time.
As such it should come with a hologram type sticker on the packaging that is intended to be placed on the newly built computer somewhere.
It contains the product key text.
A retail product will have the product keys inside the packaging, I say keys because the retail version of Win 7 includes both a 32 bit and a 64 bit DVD.
If you have bought a genuine DVD from your boss it should have come with a product key(s).
If he simply made a copy of his DVD then it is a pirate copy by default and the key he has for his original
won't work with your copy.
If he supplied you with a multiple install DVD (meant to be installed on multiple machines in his business) then he should have the key.
There are tools available that will search then registry of an installed system and display the product key.
I don't know of any tool to access the key on a disk because there is no product key on the install disk.
With the possible exception of the above mentioned unattended install OEM disk.
Think about it why would MS place the product key on an install DVD or CD for someone to extract.
BTW, regardless of whether you buy a full retail, OEM, upgrade or Multiple version of Win 7, what you are doing is buying a license(s).