What make is the laptop? and from what type of DVD are you going to reinstall? because if using (most of the big) manufacturers DVD's you do not need the product key. You will also not need a key if you perform a system recovery.
Also note that the individual product key on the sticker on bottom of laptop is different to the mass one used for pre-activated oem factory installs. The pre-activated oem factory key cannot be used for an ordinary install as it won't be accepted AFAIK
This thread on HP has good info on what end users are faced with when trying to install with the 'mass' oem factory key. scroll down to posts halfway down.
The key found by SIW is (as stated earlier)a mass product install key from the manufacturer's and will not match what was on your sticker.
Making an image of your disk with Acronis circumvents the need for a key as you just restore the image (similar to a factory reset but to the date you made the image) thus no need to worry about reinstalling everything from scratch.
If the key found by SIW and/or MagicalJellyBean is the mass factory pre-activated product key then it is a different key to the one on the sticker that you can no longer read. So the Product Key that was on Sticker is lost forever if you can't read it.
If at some time in past the op sys has been reinstalled using the key on the sticker then they will match. So SIW and/or MagicalJellyBean will retrieve it from your working installation on C: drive
My apologies for assuming that your reason for wanting the product key was for re-installation purposes, obviously if you have Acronis images you have no need to install from dvd.