Does it appear when you enter the BIOS? If so, it is likely a display defect and you'll need to replace the screen. If not, you may be able to remove it by performing a clean install of your video driver.
What version NVIDIA driver are you currently running?
When the line appears in the BIOS, the OS along with the NVIDEA video drivers are not loaded. This means there is no software fix for this issue in Windows 7. It is most likely a display defect and requires a display replacement to resolve.
How long have you had this laptop? Are you still within the time period of your retailer's return or exchange policy. If so, I recommend you try to exchange your defective laptop for a new unit or return it for a refund. If you RMA this system, it then becomes yours with its problems and you will need to RMA it to ASUS for warranty repair. It's best to exchange for a new unit or get your money back. Let ASUS and the retailer worry about fixing this problem.
If you are past your retailer's exchange/return policy, then RMA is your only option unless you wish to pay for the repair at a qualified shop or do the work yourself.