First see if the Hidden restore partition still exists. Look in: click on Start Globe, rightclick on Computer, click on Manage, Storage, Disk Management, and wait for the righthandside pane to display your Hard drive partitions.
I found this: click here f9 to get into the factory restore menu. I gather that sometimes ASUS has a thing called boot booster which may get in the way. If f9 doesn't work after a few goes tap F2, I think, to get into the BIOS. Turn Boot Booster off then try F9.
Ms Ladybird, If your F9 still doesn't work, post back as there are several other alternatives to try.