If you receive this message :
“Microsoft Lync 2010 cannot start. The product license may be expired because you are using a pre-release or evaluation copy of the program, or the product key information may have been modified in your Windows registry. Please uninstall and then reinstall Lync.
then you have used the wrong installer. Probably you used the lynceval.msi, which is the evaluation version. So what you have to do is download the correct version, for example from the MSDN site after logging in with your account.
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