HD says it's a different model than the sticker says it is. one says it is a 32bit, the other says it's a 64bit. yes the HD came out of another Acer #7731, and went into a 7741z. the 7731 got it's screen broken so I just pulled out the HD from a 7741z we had running with win7 and it worked just fine till I tried to install a new printer.Brother and HP finally gave up trying to help saying it was a glitch with win7. That's when I remembered I'd switched out the HD long ago. this is a Bussness machine with all the little add-ons that whould take for ever to put back on and I rather on have to format the drive if you know what I mean. I don't have Recovery disks for the 7731, and the ones for the 7741z won't work in this case. any suggestions ? thanks Doug