I supplied a customer with a new PC system and installed an new OEM version Windows 7 Home Premium. After installation and before delivery to the customer I activated windows. My customer is now telling me that the machine is asking for activation via entry of the product key. When the product key is entered (key taken from COA which I fixed to the machine) the software says the product key is invalid. This cannot be true because the same key was used to install Win 7 in the first place. I wonder if this is because the OEM version of Windows 7 I purchased had not got service pack 1 on the DVD when I purchased it. SP1 was installed when I did all of the updates before delivery of the machine. Maybe I forgot to activate the installation before delivery and so the installation has gone beyond the 30 day activation period. If this is the case why won't the installation recognise the valid product key? No hardware changes have been made. How can I re-activate the software?