Have you tried to recover the notebook from the hidden recovery partition on the hard drive?
Press F8 repeatedly as you switch on and this screen should appear
Select Repair Your Computer and follow the instructions. If it doesn't work contact the official support The TechGuys if it is still in warranty (12 months)
The loss of the key is not an immediate a problem as the factory installation will use common key but should have been written down as the stickers often get damaged.
Without it you do not have a "legal" copy of the operating system.
It may be possible for The TechGuys to find the key from the serial number of the notebook.
THAT WAS A WASTE OF MY TIME HAVING READ YOUR OTHER POST.
The symptoms described here viewtopic.php?f=1&t=7096&p=18952#p18952
would suggest the hard drive has failed.
Try downloading Drive Fitness Test from HGST, burn to CD and check the drive