PLEASE HELP...restoring my computer

hey guys..

u must all please forgive me as im not that smart when it comes to computers....so iv come for help from you kind and smart people.
my problem is.... my lovely but not so street wise girlfriend has spent my money (lol) on a computer from ebay an AcerPower 1000, i think or hope it was cheap.
my problem is that unknown to her, even though it was in the item discription!!!! the computer was an old network school computer and when we turn it on it wants us to add user names and password, which we obv cant.
My Question to all u amazing people is.....How do i reboot to factory setting or what are my options. please remember if u reply, u are talking to a complete computer idiot lol

hope someone can help

Matt :?

 

alt f10 as soon as you see the acer logo when putting computer on

 

thanks..is that all i have to do...will it then be straight forward.

thanks for getting back to me

Matt