Just reinstall Windows from your installation disk. When it complains about not activating, call Microsofts free activation issues phone for a new license code. That's only free if you have a retail disk. An OEM disk needs a new license, but it's possible it won't even install.
Kees
I bought new system unit which is compatible in the old one HDD, after replacing the HDD (for upgrading purpose) the win7 OS wont load when win7 logo appears, what might be the problem?

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