You could always try skipping the part where it asks for the key (you have 28 days in which to activate windows)
Once installed if the "activate on line" option doesn't work try the phone option to authenticate
To Activate by Phone -
Open the Start Menu, and type slui.exe and press Enter.
If prompted by UAC, click on Yes.
Click on the drop down menu and select the nearest location to you for a toll free number to call, then click on the Next button.
A local phone number should apear under the section with a set of installation ID numbers generated by Windows and displayed on your screen
Call the activation phone number
The activation line will be automated, so you will be asked to enter or speak the installation ID numbers displayed on your screen into the phone