If the system doesn't detect the drive, unplug, remove or disconnect the battery and hold the power button for 30 sec. Remove the base cover and hard drive; reconnect the drive. Power on, press F2 and check to see if the drive is detected. If it is, restart, press F12 and boot to the Dell diagnostics. Run an extended test on the hard drive. If it fails -- or if it's not detected, it'll need to be replaced. Hard drives -- even solid state drives - are available at or under the $100 price point.
Windows 10 is digitally connected to the system if it's been activated. You can get Windows 10 by ISO from MIcrosoft and it'll activate when you go online.
However, if the GPU and battery have both failed, you're looking at a total of far more than the system is worth to repair the system -- if the GPU fails, the mainboard needs replacement. Multiple failures mean it's time to shop for a replacement system.