how can I delete it
Contact Microsoft for activation. Activation and registration of a Microsoft product
In the interim, go to Start -> cmd.exe
In the Windows Command Prompt, type slmgr /dlv
This will display full licensing information about your operating system.
You can re-arm the operating system up to 3 times for 30-days each in the event of a genuine activation problem. You can perform this task by using slmgr -rearm in the same Command Prompt. This is not recommended unless absolutely necessary. After these run out, you face major restrictions on the use of your operating system from Windows Genuine Advantage and the built-in anti-piracy protection.
Contact your Microsoft representative or automated activation number to resolve this issue. If you suspect that the key was pirated, visit Protect Yourself from Piracy
This forum is not for discussing ways to bypass activation, violate copyright or intellectual property, get free Windows 7 product keys, or anything of the sort. If this is not a genuine problem, you need to stop wasting people's time. Otherwise, if you buy a product and it doesn't work, what do you do? You contact the person who sold it to you.