Solved Windows 7 Pro activation by HP tool

[siliconbeaver]

Desktop PC, HP Elite 8300 CMT. It was running Windows 7 Pro, GPT partition.

This weekend I did fresh-install, Windows 7 Pro, GPT (same setup). then tested the HP OEM activation tool provided by SIW2

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When done, it's noticed that PC NOT activated. The HP OEM Win7 activation tool was working on HP Elite 8200 CMT last time. no idea why this time it's NOT working.

I re-tried MBR install. But Win 7 Pro asked to format GPT first. I am NOT sure if it's worth. hence stopped.

Am I missing something? or the HP tool not working any more?
(I tried various install, with or without internet. i.e. online or offline. No help)

Thanks,

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Update

After the hdd changed to MBR partition, the HP tool is working.
i.e. the HP tool works for MBR partition.