find out wimdoes oem product key

Solution
If you can not locate the sticker, or it has been damaged, and your machine is able to boot into Windows, you should be able to use a utility such as Magical Jelly Bean Keyfinder:

http://www.magicaljellybean.com/keyfinder/

The name may sound silly, but the free download should be more than sufficient to find a few keys on your system, such as Windows.
If you can not locate the sticker, or it has been damaged, and your machine is able to boot into Windows, you should be able to use a utility such as Magical Jelly Bean Keyfinder:

http://www.magicaljellybean.com/keyfinder/

The name may sound silly, but the free download should be more than sufficient to find a few keys on your system, such as Windows.
 
Solution
windows 8 keys don't come on a label and therefore you wont find one on your computer. fyi they are all built into and encrypted in the bios by all major manufactures so that the key is tied to the motherboard and therefore the computer itself (anti piracy feature by Microsoft)
 
-Having a key to use windows is a Microsoft requirement.
-How the key is provided is up to the vendor of the hardware