Have just purchased a Lenovo Keyboard with fingerprint reader, which driver do I need and where do I get it, using Windows 7
Did it not come with a disk? Lenovo is pretty good about that.
That said, if you'd take the time to Google "lenovo usb keyboard with fingerprint reader" the first hit that comes back is their product page (I am assuming this is what you have since I think they're only shipping the one) which has a link at the bottom to "Software and device drivers".
Google is your friend - learn to help yourself and you'd be amazed how productive you can be. ;)