How to get product code for windows 8

I have a friend whose Aspire R7-571 has had a hard disk problem, and he is in the process of order the restore disks to reinstall WIndows 8 and other software. In the meantime I would like to install a copy of WIndows 8 from Microsoft on it, but there is no product code sticker on the laptop and it does not seem to be anywhere in the paperwork he got when it was given to him as a gift. Is there a number I can call at Acer to get this information? I was able to make an image of the files on the disk if that helps. Thank you.