Window's Problem w/ Validation

Okay.
I have a computer here which hasn't had any updates done by Windows in a long time.
I tried to do it and it asked me to pass validation.
When I tried, it failed validation.
I checked the first issue that could be the problem and this is it:

The last five digits the website reported were 3TW6T.
The last five digits on my computer's cerificate of authenticity is 3W4MB...

Now when I enter the "correct" product key into the "Windows Product Key Update Tool" program, I get the following error:

What should I do?
I checked it over five million times. No mistakes.

 

Just call Microsoft and explain the problem. You may be on hold for a while, but I have always gotten things straightened out after some time.

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Hey.

I was trying to do this, but I didn't have any luck finding the phone number for Microsoft Support ...