Unfortunately the labels never say whether the OS is 32-bit or 64-bit, though the keys are interchangeable
32 bit iso can be downloaded from
http://msft.digitalrivercontent.net/win/X17-58996.iso 64 bit iso
http://msft.digitalrivercontent.net/win/X17-58997.iso
Burn the ISO to DVD, and use it along with a USB DVD drive to boot the machine and reinstall windows
I expect that you won't be able to activate the product key online, but will have to phone Microsofts robot to do it. Thats normal for an Acer product key
edit
both 32-bit and 64-bit drivers are online from Acer at
http://www.acer.co.uk/ac/en/GB/content/drivers just follow the path through the grid
netbook > Aspire One > AO722 > operating system