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To do this, right-click on C:\Program Files (x86)\PuTTY\puttygen.exe and select Run as Administrator:
Answer "Yes" to the User Account Control challenge. Then click the "Generate" button in the puttygen window. puttygen will ask you to move your mouse over its dialog box to generate random seed bits. After it has computed a public key, it will display a dialog box resembling the following:
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