Tried web activation and Phone activation, too. It can't be done.

In addition, I read some folks here having the same problem and tried different ways, but no go.

Hi,

According to your description, this issue is that the product key is considered invalid since the System upgrade. Since you have tried web activation and Phone activation, I suppose that the activation count might be exhausted.

 I suggest you contact the customer service, explain the scenario to them and ask if they can provide some help:

http://support.microsoft.com/gp/customer-service-phone-numbers/en-us

Regards,

George Zhao
TechNet Community Support