Although you mentioned that you're missing options in the bios, see if you can locate the boot options, and put HDD as 1st on the list. Also take out a CD and usb drives if you have any connected.
Next you'd want to check for hard drive health.You can try finding a hard drive diagnostics test in the bios. Alternatively you can download a bootable diagnostics utility from ASUS, you'll need to put it on a CD/USB and load from that. Lastly you can take out the harddrive from the laptop and either put it into a different laptop or connect it through an external adapter to another machine to see if it reads and also grab any data from it if needed.
Depending if the problem is with the hardware related you would need a replacement drive. If issue is with software corruption you'd need to reinstall the OS.
Hope this helps and good luck!