I've got an older laptop that I bought second hand. It came with Windows 7 on it and it has the sticker with the product code inside the battery compartment. The trouble is that one digit has worn off completely and another is partly worn. Is there any way of figuring out what the missing digits might be? I could try reinstalling onto a spare hard drive and trying all the permutations (the partly worn one looks like an O/0 or a D, so it's not like I've got thousands of possibilities. If there is a way of figuring the missing value that would be great.
I know it will install but can you actually activate the OS on a different drive even if you find the missing value? Each drive having it's unique id marker?
I believe you can install on a different drive as long as it's the same computer, more or less. Ideally I'll clone the drive but if I have any problems it would be good to have the product code as a fallback. A lot depends on whether the license is the full version or the OEM. It always used to be (and I think it still applies for Win7) that the OEM version is registered to a specific PC and is sensitive to changes to the PC. Upgrading a hard drive, memory etc is the kind of thing it's reasonable for any computer owner to do but if you do things like change the motherboard it's considered a different PC and won't validate. The full retail version (which could be anything up to 2-3 times the price of the OEM, if I recall) was more forgiving about transferring to another PC. I'm not sure what, if anything, they did to make sure it was actually deactivated from its previous host before installing on a new host but it could have been something as simple as the old one being locked out as soon as it tried to do anything involving an internet connection or something.