Asus x540SA notebook. 4GB ram, 500GB HDD
If we can get you into the system, you will not need to return the laptop for repair. From personal experience, ASUS will charge you approximately $200 to reload the HDD. ASUS should have a single push button process to access the recovery partition, at least they did prior to Windows 10. You should not need the product key for this process. Cross your fingers this has not changed.
Please try the following and let us know if this works to access the recovery partition:
Restart the computer and as soon as you see the ASUS logo display on the screen, start tapping or hold the F9 key on the keyboard. This should bring you to a screen where you select Windows Setup (EMS enabled). This should take you to a menu that shows the various partitions on your computer where you can select the recovery the partition. I am not sure what that screen looks like so if you are not sure what to select, do nothing and stop to ask for our help. Post what partitions you see and we can guide you from there.