Last week I had some issues convincing my machine that it could indeed run the WGA tool

I came across a bunch of genuine advantage tips and tricks to help along the way:

http://forums.microsoft.com/Genuine/ShowPost.aspx?PostID=956524&SiteID=25

Please download and run: http://go.microsoft.com/fwlink/?linkid=69498
- this is the latest WGA Notifications file.

Afterward, login as administrator and head to www.microsoft.com/genuine and click Validate Windows.

I am still working on the following issue however:
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Windows Genuine Advantage
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Code not available. The validation code could not be obtained. This may be due to technical difficulties, or you may be running an unsupported operating system. Please close this window and attempt the validation process again, or use the Back button in your Web browser to return to the download details page. [Error code: 0x80072f19]
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OK  
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Update: Alin Constantin writes in this forum post:

"As for the 0x80072F19, it means ERROR_INTERNET_SEC_CERT_REV_FAILED."