https://support.microsoft.com/en-us/...tech-services/
This is a good place to start. They have chat.
I used Belarc Advisor to find out the product key---it's 25 digits. I turned the 4 page report into a pdf and emailed it to myself.
This is how to get a copy of windows 8.1 or 10 to install on a hard drive.
1. Please access this link
Download Windows 8.1 Disc Image (ISO File)
2. Click on download tool now
3. Click on Run and make sure the USB is blank and at least more than 4GB
4. Then accept the terms and Condition
5. Click on create a bootable device for another PC
6. Click on next, then choose the USB where the file would be burn
7. Wait for the Download to complete then follow the steps below.
Change the Boot priority from to USB
1. Plugged in the USB
2. Turn off PC, then while restarting it please press f2 repeatedly
3. Then choose the boot priority to USB
4. Then follow the following steps below to reinstall windows 8 or 10
How to Clean install windows 8 or 10
1. Keep the USb plugged in
2. Restart the PC
3. Once the Manufacturer's logo appeared, press any keys.
4. Choose language, time and currency format and Keyboard input method.
5. Choose Install
6. Enter or Skip the Activation part.
7. Accept the License Term and click Next.
8. Choose the drive where the OS is installed