Thanks for the replies!
Booglebox wins the prize - worked a treat, she now has a fully functional laptop again, and is chuffed about it! Not sure, but I think it went into Windows recovery options rather than an Acer specific recovery. I will find out exactly what she did when I next speak to her and will post back here. I will also remember that bit of advice as I have Win 8.1 too. Cheers!