Hi, thanks for your answer. I contacted Acer before, but they said I would have to buy recovery disks..... The problem is that until I install windows again there's nothing to recover! Bit of a chicken and egg job..... I might try Acer and Microsoft again though to ask specifically about this product key issue.
As the product key is linked to the motherboard, you'd think there must be a way to trace it by the serial number?