When I got my laptop (Acer Aspire E1-510) it came with Windows 8. I had some really bad lag with this computer so it was recommended I go to Windows 7 which I did. Now, I want to try and re-install Windows 8, however, I do not have a product key... Is there any way to recover it?
You may want to hit Acer with an email to confirm but I'm pretty sure the Windows 8 product key is embedded in the BIOS (firmware) of the computer.
So if you have the installation media or created the system recovery DVDs as suggested when you first brought it home you should be good to go.
If not then you may need to ask Acer for their recovery media for your specific laptop.
EDIT: Additionally, depending on how you went about installing Windows 7, you may still have the factory recovery partition on your system's hard drive, in which case you may be able to use that for a factory reset.
Of course, backup any critical data before you go forward with the process.