After installing DHCP on Windows Server 2008 R2, you may start to see the following error message in the event logs:

Volume Shadow Copy Service error: Unexpected error calling routine RegOpenKeyExW(-2147483646,SYSTEM\CurrentControlSet\Services\VSS\Diag,...). hr = 0x80070005, Access is denied.

Inspection of the detailed tab of the event log entry will show information about the process that generated the error.
To resolve this error, simply give NETWORK SERVICE full permission to the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\VSS

Let me know if this helped you, or if your server is still generating an error.