I've got the same problem. I had to format my Laptop due to a virus, and reinstall all my programmes. Unfortunately, I had thrown away my AutoCAD 2007 Lt packaging prior to this (thinking the serial number was on the back of the CD Case like many other software titles I own), and cannot remember who the vender was that I ordered my disc from (it was some time back)!!!
How can I get the Serial Number now???
Many Thanks,
Mike