|Does the screen appear to be working correctly when in Safe Mode? If so, you may need to change the graphics driver. You may be able to roll back the driver to a previous version. |
I am not sure what your sister may have done. I personally don't know of a program that splits the screen into 8 segments.
To rollback or to update the graphics chip while in Safe Mode right click on My Computer> properties> hardware> device Manager. Expand Display Adapters and right click on the adapter listed there. Choose properties and try the troubleshooter. If no go then at the same screen choose drivers and rollback. If that doesn't help you may need to update the graphics driver. To obtain the correct driver for your laptop go to the link below and choose the EXACT model and follow the prompts to download the correct drivers.
If you boot into Safe Mode with Networking you should be able to download directly to the laptop.