You might have a boot-loader virus on your laptop which can be hard to get rid of even after you've reformated your hard drive. I would suggest using a partitioning tool like G-parted and just nuke the drive entirely here's a link to G-parted. http://gparted.sourceforge.net/
Just download the G-parted ISO and burn it to a CD and then you'll boot from it and then you can delete your hard drive and then try reinstalling the OS. Also your unit might be defective and you may need to send it in to ASUS for a warranty service.