If you use Windows 7 Pro/Ultimate/Home Premium non sp1:

You only the way to activate Windows 7 is activation by phone.
Note: Windows 7 Pro sp1 and Windows 7 Pro non sp1 use different keys to activate.
This is Windows 7 Pro sp1 (You will see Server Pack 1 below Windows 7 Professional)

How to activate Windows 7 by phone
Step 1: You select “change product key” then you copy and paste the key you buy from me => Next
Step 2: You will see the error “0x80072f8f”
You select “Show me the other ways to activate”

Then you select “Use the automated phone system”

Then you select your local => Next

Then you call to number

After you call, you have confimation ID the phone system give you. You copy paste it and click “Next”