Hello and welcome to the forum.
my Acer laptop has been running windows 8.1 since i bought it new yesterday
A one day old laptop that is now unusable?
It would seem that this Windows 10 upgrade is a gift that just keeps on giving.
I believe that Acer products come with a factory partition and a built in utility (F10 at the Acer Screen I believe).
That will allow you to reset the laptop to factory fresh condition without any password prompts.
Just going by memory here, you unit may be slightly different and require a different key but I suspect that information is available online through the Acer Community for your specific make and model if different.
Best of luck and let us know how things progress.
Maybe give some serious consideration to the upgrade, you have a year to get it for free. They (Microsoft) are going to have to work out some of these bugs or at the very least publish some specific guidelines and tips for upgraders.