Task Sequence "Task Sequence Name" has failed with the error code (0x80070002). For more information, contact your system administrator or helpdesk operator.
This error popped up as soon as the "Apply Operating System" action kicked off within the task sequence. The "Apply Operating System" task attempts to download the Windows 7 Enterprise WIM file from the closest deployment point, however will experience access issues if no network access account has been configured yet. The operating system deployment process running of PXE boot requires access back to SCCM to download the operating system WIM file.
To configure the network access account, under Administration, Sites, Configure Site Components, select Software Distribution.
On the Network Access Account tab, supply SCCM with a network access account which has permissions to connect to the distribution point repository.
Hope this post has been helpful.